Methods for sending small packets in a peer-to-peer (P2P) network

ABSTRACT

An improved mechanism is provided that facilitates transmission of small packets within an ad hoc peer-to-peer network. A small packet is identified to a receiver within a control channel so that its lower power can be considered in an interference management protocol implemented among local peer devices. In a traffic slot, a transmitter voluntarily backs down on the transmitter power as a smaller packet will require much lower signal-to-noise ratio. This will improve the signal energy per bit per noise power density for the transmission as well as minimize the interference caused to other wireless communications happening in the same spectrum.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent claims priority to U.S. ProvisionalApplication No. 60/948,654 entitled “Method and Apparatuses Relating toPeer to Peer Communications” filed Jul. 9, 2007, and assigned to theassignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

1. Field

The present invention relates to wireless communication within apeer-to-peer network and, in particular, to methods by which a mobileterminal may send small amounts of data to an intended receiverterminal.

2. Background

In a wireless network, e.g., an ad hoc network, in which a networkinfrastructure does not exist, a terminal has to combat certainchallenges in order to set up a communication link with another peerterminal. One challenge is that when a terminal just powers up or movesinto a new area, the terminal may have to first find out whether anotherterminal is present in the vicinity before any communication between thetwo terminals can start.

Due to the lack of the network infrastructure, terminals in an ad hocwireless network may often not have a common timing reference or networkcontroller which can assist in traffic management. So it is possiblethat when a first terminal is transmitting a signal and a secondterminal is not in the receiving mode, therefore the transmitted signaldoes not help the second terminal to detect the presence of the firstterminal. Power efficiency has great impact on the battery life of theterminals and is thus another important issue in the wireless system.

Additionally, a plurality of wireless terminals may operate in anenvironment while sharing a frequency spectrum to establish ad hocpeer-to-peer communications. Because such ad hoc peer-to-peercommunications are not centrally managed by a centralized controller,interference between multiple peer-to-peer links among nearby wirelessterminals is problem. That is, transmissions from a wireless terminalmay cause interference with other unintended receiver wirelessterminals.

Significantly, power efficiency has a great impact on the battery lifeof the wireless terminals and thus presents another challenge inwireless systems. Existing peer to peer systems typically employ asimple fixed power arrangement for simplicity. Under such anarrangement, a transmitter uses a fixed traffic transmission powerregardless the distance of the intended receiver and the channelcondition. A fixed power system, however, suffers from poor powerefficiency and reduced overall throughput due to signal interference.

Additionally, a plurality of wireless terminals may operate in anenvironment while sharing a frequency spectrum to establish ad hocpeer-to-peer communications. Because such ad hoc peer-to-peercommunications are not centrally managed by a centralized controller,interference between multiple peer-to-peer links among nearby wirelessterminals is problem.

Consequently, a solution is needed to permit peer-to-peer communicationsa shared frequency spectrum while reducing unwanted interference toother wireless terminals.

SUMMARY

In one example, a second device is provided having a peer-to-peerconnection with a first device to facilitate interference management ofsmall packet transmissions using flash signaling within an ad hocwireless network. The second device may receive a signal in a pluralityof predetermined subsets of resource units. A first phase to be used ina desired signal in each of the plurality of predetermined subsets ofresource units is then calculated, where the desired signal being sentby the first device. The second device then determines one resource unitin each of the plurality of predetermined subsets of resource units inwhich the desired signal is sent as a function of the received signaland calculated first phase. Information bits transported in the desiredsignal may be recovered from the location of the determined one resourceunit in each of the plurality of predetermined subsets of resourceunits.

The calculated first phase may be the same in each of the plurality ofpredetermined subsets of resource units and is generated from at leastone of a first identifier of the first device, a second identifier ofthe second device, and an identifier of the peer-to-peer connectionbetween the first and the second devices. The calculated first phase maybe determined as a function of a predetermined sequence, the calculatedfirst phase being different in the different predetermined subsets ofresource units. A power to be used in the desired signal in each of theplurality of predetermined subsets of resource units may be calculatedby the second device, where the calculated power is determined as afunction of a predetermined sequence, the calculated power beingdifferent in the different predetermined subsets of resource units, andwherein the one resource unit is determined also as a function of thecalculated power. The second device also calculates a second phase to beused in an interference signal in each of the plurality of predeterminedsubsets of resource units, the interference signal being transmitted byan interfering device; and wherein the one resource unit is determinedalso as a function of the calculated second phase. The predeterminedsequence may be generated from at least one of a first identifier of thefirst device, a second identifier of the second device, and anidentifier of the peer-to-peer connection between the first and thesecond devices.

In another example, a first device is provided having a peer-to-peerconnection with a second device to facilitate interference management ofsmall packet transmissions within an ad hoc wireless network. The firstdevice partitions a set of resource units into a plurality ofpredetermined subsets of resource units. It then determines one resourceunit in each of the plurality of predetermined subsets of resource unitsas a function of a set of bits. The first device then transmits a signalin the determined one resource unit in each of the plurality ofpredetermined subsets of resource units. The set of bits may begenerated from a set of information bits with an encoder. The phase ofthe transmitted signal in the determined one resource unit may be thesame in each of the plurality of predetermined subsets of resource unitsand may be generated from at least one of a first identifier of thefirst device, a second identifier of the second device, and anidentifier of the peer-to-peer connection between the first and thesecond devices.

The first device may also generate a plurality of phases as a functionof a predetermined sequence, wherein the phase of the transmitted signalin the determined one resource unit in each of the plurality ofpredetermined subsets of resource units is equal to one of the generatedplurality of phases. The predetermined sequence is generated from atleast one of a first identifier of the first device, a second identifierof the second device, and an identifier of the peer-to-peer connectionbetween the first and the second devices.

The first device may also generate a plurality of generating a pluralityof power values as a function of a predetermined sequence, wherein thepower of the transmitted signal in the determined one resource unit ineach of the plurality of predetermined subsets of resource units isequal to one of the generated plurality of power values.

The various features describe herein may be implemented within awireless device, a circuit or processor incorporated in a wirelessdevice, and/or a software.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features, nature, and advantages may become apparent from thedetailed description set forth below when taken in conjunction with thedrawings in which like reference characters identify correspondinglythroughout.

FIG. 1 is a block diagram illustrating the how an ad hoc peer-to-peernetwork may be implemented, e.g., in conjunction a wide area network.

FIG. 2 is a block diagram illustrating an environment in which aplurality of wireless terminals may establish peer-to-peer communicationconnections that may cause interference to other nearby wirelessterminals.

FIG. 3 illustrates one example of a transmission channel architecturethat may be used by wireless terminals to transport control signalingand traffic for a peer-to-peer communication connection between wirelessterminals.

FIG. 4 illustrates an example time-frequency grid that may be used insignal transmissions over the channel architecture of FIG. 3.

FIG. 5 is a flow diagram illustrating the operation of various wirelessterminals in an ad hoc peer-to-peer network that facilitates connectionscheduling where a plurality of wireless terminals share a communicationchannel.

FIG. 6 is a flow diagram illustrating how transmit power scaling may beimplemented for a peer-to-peer connection between two wirelessterminals.

FIG. 7 illustrates an example of how power may be reduced whentransmitting a small packet in a peer-to-peer network.

FIG. 8 illustrates a method operational at a second device having apeer-to-peer connection with a first device to facilitate interferencemanagement of small packet transmissions using flash signaling within anad hoc wireless network.

FIG. 9 illustrates a method operational at a first device having apeer-to-peer connection with a second device to facilitate interferencemanagement of small packet transmissions within an ad hoc wirelessnetwork.

FIG. 10 (comprising FIGS. 10A and 10B) illustrates a method of operatinga first wireless device in a peer-to-peer communication network.

FIG. 11 illustrates a method of operating a second wireless device in apeer to peer communication network.

FIG. 12 illustrates a method of operating a third wireless device in apeer to peer communication network.

FIG. 13 (comprising FIGS. 13A and 13B) illustrates a method operationalin a third device having a peer-to-peer connection with a fourth deviceto facilitate interference management for a second peer-to-peerconnection between a first device and a second device within a wirelessnetwork.

FIG. 14 (comprising FIGS. 14A and 14B) illustrates a method operationalin a fourth device having a peer-to-peer connection with a third deviceto facilitate interference management for a second peer-to-peerconnection between a first device and a second device within a wirelessnetwork.

FIG. 15 illustrates a method of operating a second wireless device in apeer-to-peer communication network, the second wireless device having aconnection with a transmitter first wireless device.

FIG. 16 illustrates a method of operating a second wireless device in apeer-to-peer communication network, where the second wireless device hasa connection with a transmitter first wireless device.

FIG. 17 is a block diagram of a first wireless terminal that may beconfigured to facilitate peer-to-peer communications with a secondwireless terminal over a shared frequency spectrum.

DETAILED DESCRIPTION

In the following description, specific details are given to provide athorough understanding of the configurations. However, it will beunderstood by one of ordinary skill in the art that the configurationsmay be practiced without these specific detail. For example, circuitsmay be shown in block diagrams in order not to obscure theconfigurations in unnecessary detail. In other instances, well-knowncircuits, structures and techniques may be shown in detail in order notto obscure the configurations.

Also, it is noted that the configurations may be described as a processthat is depicted as a flowchart, a flow diagram, a structure diagram, ora block diagram. Although a flowchart may describe the operations as asequential process, many of the operations can be performed in parallelor concurrently. In addition, the order of the operations may bere-arranged. A process is terminated when its operations are completed.A process may correspond to a method, a function, a procedure, asubroutine, a subprogram, etc. When a process corresponds to a function,its termination corresponds to a return of the function to the callingfunction or the main function.

In one or more examples and/or configurations, the functions describedmay be implemented in hardware, software, firmware, or any combinationthereof. If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above are also beincluded within the scope of computer-readable media.

Moreover, a storage medium may represent one or more devices for storingdata, including read-only memory (ROM), random access memory (RAM),magnetic disk storage mediums, optical storage mediums, flash memorydevices and/or other machine readable mediums for storing information.

Furthermore, configurations may be implemented by hardware, software,firmware, middleware, microcode, or any combination thereof. Whenimplemented in software, firmware, middleware or microcode, the programcode or code segments to perform the necessary tasks may be stored in acomputer-readable medium such as a storage medium or other storage(s). Aprocessor may perform the necessary tasks. A code segment may representa procedure, a function, a subprogram, a program, a routine, asubroutine, a module, a software package, a class, or any combination ofinstructions, data structures, or program statements. A code segment maybe coupled to another code segment or a hardware circuit by passingand/or receiving information, data, arguments, parameters, or memorycontents. Information, arguments, parameters, data, etc. may be passed,forwarded, or transmitted via any suitable means including memorysharing, message passing, token passing, network transmission, etc.

One feature provides a transmitter wireless terminal configured toestablish a peer to peer communication link with a receiver wirelessterminal over a shared communication channel. The transmitter wirelessterminal may scale its transmit power as a function of a channel gainfor the communication channel between the transmitter and receiverwireless terminals. The scaled transmit power may be utilized by thetransmitter and receiver wireless terminals to perform link schedulingover the communication channel. For instance, the scaled transmit powermay be used by the transmitter wireless terminal to perform atransmitter yielding with other neighboring transmitter wirelessterminals utilizing the shared communication channel. Similarly, thescaled transmit power may be used by the receiver wireless terminal toperform receiver yielding with other neighboring receiver wirelessterminal utilizing the shared communication channel.

Another feature provides an improved mechanism that facilitatestransmission of small packets. In a traffic slot, a transmittervoluntarily backs down on the transmitter power as a smaller packet willrequire much lower SNR. This will improve the signal energy per bit pernoise power density (E_b/N_(—)0) for the transmission as well asminimize the interference caused to other wireless communicationshappening in the same spectrum. The fact that a small packet is beingtransmitted can be signaled in a control channel so that the otherpeer-to-peer devices can use this information for their scheduling andrate prediction algorithms.

Ad Hoc Communication System

An ad hoc peer-to-peer wireless network may be established among two ormore terminals without intervention of a centralized network controller.In some examples, the wireless network may operate within a frequencyspectrum shared among a plurality of wireless terminals.

FIG. 1 is a block diagram illustrating the how an ad hoc peer-to-peernetwork may be implemented, e.g., in conjunction a wide area network. Insome examples, the peer-to-peer network and the wide area network mayshare the same frequency spectrum. In other examples, the peer-to-peernetwork is operated at a different frequency spectrum, e.g., a spectrumdedicated to the use of the peer-to-peer network. A communication system100 may comprise one or more wireless terminals WT-A 102, WT-B 106, andWT-C 112. Although just three wireless terminals WT-A 102, WT-B 106, andWT-C 112 are depicted, it is to be appreciated that communication system100 may include any number of wireless terminals. The wireless terminalsWT-A 102, WT-B 106, and WT-C 112 can be, for example, cellular phones,smart phones, laptops, handheld communication devices, handheldcomputing devices, satellite radios, global positioning systems, PDAs,and/or any other suitable device for communicating over wirelesscommunication system 100.

According to one example, the communication system 100 may support awide area network (WAN) which may include one or more access nodes AN-A104 and AN-B 110 (e.g., base station, access point, etc.) and/or anynumber of disparate access nodes (not shown) in one or moresectors/cells/regions that receive, transmit, repeat, etc., wirelesscommunication signals to each other and/or to the one or more wirelessterminals WT-A 102, WT-B 106, and WT-C 112. Each access node AN-A 104and AN-B 110 may comprise a transmitter chain and a receiver chain, eachof which can in turn comprise a plurality of components associated withsignal transmission and reception (e.g., processors, modulators,multiplexers, demodulators, demultiplexers, antennas, . . . ) as will beappreciated by one skilled in the art. According to an optional feature,when communicating through the WAN, the wireless terminal(s) maytransmit signals to and/or receive signals from an access node whencommunicating via the wide area infra-structure network supported by thecommunication system 100. For instance, wireless terminals WT-A 102 andWT-B 106 may communicate with the network via access node AN-A 104 whilewireless terminal WT-C 112 may communication with a different accessnode AN-B 110.

The wireless terminals may also communicate directly with each other viaa local area peer-to-peer (P2P) network (e.g., ad hoc network).Peer-to-peer communications may be effectuated by directly transferringsignals between wireless terminals. Thus, the signals need not traversethrough an access node (e.g., a base station) or centrally managednetwork. The peer-to-peer network may provide short range, high datarate communication (e.g., within a home, office, etc. type setting). Forexample, wireless terminals WT-A 102 and WT-B 106 may establish a firstpeer-to-peer network 108 and wireless terminals WT-B 106 and WT-C 112may also establish a second peer-to-peer network 114.

Additionally, each peer-to-peer network connection 108 and 114 mayinclude wireless terminals within a similar geographic area (e.g.,within range of one another). However, it is to be appreciated thatwireless terminals need not be associated with the same sector and/orcell to be included in a common peer-to-peer network. Further,peer-to-peer networks may overlap such that one peer-to-peer network maytake place within a region that overlaps or is encompassed with anotherlarger peer-to-peer network. Additionally, a wireless terminal may notbe supported by a peer-to-peer network. Wireless terminals may employthe wide area network and/or the peer-to-peer network where suchnetworks overlap (e.g., concurrently or serially). Moreover, wirelessterminals may seamlessly switch or concurrently leverage such networks.Accordingly, wireless terminals whether transmitting and/or receivingmay selectively employ one or more of the networks to optimizecommunications.

Peer-to-peer communications between the wireless terminals may besynchronous. For example, wireless terminals WT-A 102 and WT-B 106 mayutilize a common clock reference to synchronize performance of distinctfunctions. The wireless terminals WT-A 102 and WT-B 106 may obtaintiming signals from the access node AN-A 104. The wireless terminalsWT-A 102 and WT-B 106 may also obtain timing signals from other sources,for instance, GPS satellites or television broadcast stations. Accordingto an example, time may be meaningfully partitioned in a peer-to-peernetwork for functions such as peer discovery, paging, and traffic.Further, it is contemplated that each peer-to-peer network may set itsown time.

Before communication of traffic in a peer-to-peer connection can takeplace, the two peer wireless terminals may detect and identity eachother. The process by which this mutual detection and identificationbetween peers takes place may be referred to as peer discovery. Thecommunication system 100 may support peer discovery by providing thatpeers (terminals), desiring to establish peer-to-peer communications,periodically transmit short messages and listen to the transmissions ofothers. For example, the wireless terminals WT-A 102 (e.g., transmittingwireless terminal) may periodically broadcast or send signals to theother wireless terminal(s) WT-B 106 (e.g., receiving wirelessterminal(s)). This allows the receiving wireless terminal WT-B 106 toidentify the sending wireless terminal WT-A 102 when the receivingwireless terminal WT-B 106 is in vicinity of the sending wirelessterminal WT-A 102. After identification, an active peer-to-peerconnection 108 may be established.

Transmissions for peer discovery may periodically occur during specifiedtimes referred to as peer discovery intervals, the timing of which maybe predetermined by a protocol and known to the wireless terminals WT-A102 and WT-B 106. Wireless terminals WT-A 102 and WT-B 106 may eachtransmit respective signals to identify themselves. For example, eachwireless terminal WT-A 102 and WT-B 106 may send a signal during aportion of a peer discovery interval. Further, each wireless terminalWT-A 102 and WT-B 106 may monitor signals potentially transmitted byother wireless terminals in a remainder of the peer discovery interval.According to an example, the signal may be a beacon signal. By way ofanother illustration, the peer discovery interval may include a numberof symbols (e.g., OFDM symbols). Each wireless terminal WT-A 102 mayselect at least one symbol in the peer discovery interval fortransmission by that wireless terminal WT-A 102. Moreover, each wirelessterminal WT-A 102 may transmit a corresponding signal in one tone in thesymbol selected by that wireless terminal WT-A 102.

The local area peer-to-peer network and the wide area network may sharea common wireless spectrum to effectuate communication; thus, bandwidthmay be shared for transferring data via the disparate types of networks.For example, the peer-to-peer network and the wide area network may bothcommunicate over the licensed spectrum. However, the peer-to-peercommunication need not utilize the wide area network infrastructure.

After wireless terminals discover each other, they may proceed toestablish connections. In some examples, a connection links two wirelessterminals, e.g., in FIG. 1 connection 108 links wireless terminals WT-Aand WT-B. Terminal WT-A 102 can then transmit traffic to terminal WT-B106 using connection 108. Terminal WT-B 106 can also transmit traffic toterminal WT-A 102 using connection 108.

Baseline Peer-to-Peer Protocol

An interference management protocol is provided that allows a pluralityof wireless terminals to operate in an environment while sharing afrequency spectrum to establish ad hoc peer-to-peer communications.Because ad hoc peer-to-peer communications are not centrally managed bya centralized controller, interference between multiple peer-to-peerlinks among nearby wireless terminals may be a problem. However, thepeer-to-peer protocol described herein facilitates establishing and/ormaintaining ad hoc peer-to-peer connections among different wirelessterminals without the assistance of a centralized controller.

FIG. 2 is a block diagram illustrating an environment in which aplurality of wireless terminals may establish peer-to-peer communicationconnections that may cause interference to other nearby wirelessterminals. A peer-to-peer network 200 may include a plurality ofwireless terminals that may share and/or concurrently use a frequencyspectrum. The shared frequency spectrum may include one or moretransmission and/or control channels, with each transmission (traffic)channel having a corresponding traffic control channel. In one example,the traffic control channel may be used to send a traffic request forcommunications over a corresponding transmission (traffic) channel.

In one example, a first wireless terminal WT A 202 may be attempting totransmit 210 to a second wireless terminal WT B 204 while a thirdwireless terminal WT C 206 is concurrently attempting to transmit 214 toa fourth wireless terminal WT D 208 using the same traffic channelbandwidth resource. The first wireless terminal WT A 202 may be referredto as the intended transmitter, the second wireless terminal WT B 204may be referred to as the intended receiver, and the third wirelessterminal WT C 206 may be considered the interferer. In this peer-to-peernetwork 200, a transmission and control channel pair may be shared bythe plurality of the wireless terminals WT A, WT B, WT C, and WT D.However, because such transmission (traffic) and/or control channel isshared (e.g., frequency spectrum sharing) by the wireless terminals, itmay also result in unwanted interference 214′ and 210′ among thewireless terminals. For instance, if both transmissions 210 and 214actually take place, then the signal 214′ from the third wirelessterminal WT C 206 may be seen as interference to the second wirelessterminal WT B 204 receiver and may degrade its ability to successfullyrecover the desired signal 210 from the first wireless terminal WT A202. Therefore, certain interference management protocol is needed tomanage interference from the third wireless terminal WT C 206 to thesecond wireless terminal WT B 204. One goal of the interferencemanagement protocol is to allow the third wireless terminal WT C 206 totransmit without creating excessive interference to the second wirelessterminal WT B 204, thereby increasing the overall throughput andimproving the system performance. Note that in the meantime, the firstwireless terminal WT A 202 may also cause interference 210′ to thefourth wireless terminal WT D 208, and a similar interference managementprotocol may also be used to control that interference.

Because there is no centralized traffic management authority, there is achance that WT A 202 and WT C 206 may transmit on the same oroverlapping channel, thereby causing interference with each other. Forexample, by coincidence, both WT A 202 and WT C 206 may use the sametransmission CID. A transmission CID may be used to indicate aparticular transmission channel (e.g., frequency or time slot) to areceiving terminal WT B 204 and 208. Consequently, when the sametransmission CID is used by two terminals, they may also be concurrentlytransmitting on the same channel or overlapping channels. If bothtransmitting terminals WT A 202 and WT C 206 are within range of thereceiver terminals WT B 204 and/or WT D 208, then the receiver terminalsWT B 204 and/or WT D 208 may perceive interference.

In particular, a way is needed that allows multiple wireless terminalsto choose channels within shared frequency the without distinguishbetween transmissions from an intended peer and those from an unintendedpeer.

According to one implementation, transmitter and/or receiver yieldingmay be implemented by devices in a peer-to-peer network that allows adevice to backoff if it is likely to cause interference to other nearbydevices of higher priority. Consequently, if the first connection 210between the first device WT A 202 and second device WT B 204 has ahigher priority than the second connection 214 between the third deviceWT C 206 and the fourth device WT D 208, the third device WT C 206 mayimplement transmitter yielding and/or the fourth device WT D 208 mayimplement receiver yielding. When yielding, a device determines whetherits transmission power will unacceptably interfere with transmissions ofother nearby devices. Such yielding may also take into account therelative priority of the different transmissions or peer-to-peerconnections associated with such transmissions. For instance, a devicemay decide to yield only if it has a lower connection or transmissionpriority than another connection or transmission.

In one example of receiver yielding, a receiving device may not send anecho or reply transmission (e.g., in response to a transmission request)if its noise-to-signal ratio is too low, thereby preventing acorresponding interfering transmitting device from sending traffic tothe receive device on the selected channel. In another example, thereceiver device may indicate that a lower transmit power should be usedby its corresponding transmitter device to avoid interference.

In one example of transmitter yielding, a transmitting device maydetermine whether its own transmissions will cause unacceptableinterference to another device utilizing a shared channel, and if so, itmay not send data transmissions on that shared channel.

In one example, wireless terminal WT A 202 may determine a transmitpower P_(A) for traffic data transmissions. Power P_(A) need not befixed and can be varied in accordance with certain criteria, such astraffic type, Quality of Service (“QoS”) conditions, for example. Incertain embodiments, the transmitter for a wireless terminal can varyits power without notifying the receiver in advance. In one embodiment,the transmit power P_(A) may be defined according to the followingequation:

$\begin{matrix}{{P_{A} = \frac{C}{h_{AB}^{\beta}}},} & \left( {{Equation}\mspace{20mu} 1} \right)\end{matrix}$where C and β are positive constants, and h_(AB) is a decimal value lessthan or equal to one (1) that corresponds to the channel gain betweenthe transmitting wireless terminal WT A 202 and the receiving wirelessterminal WT B 204. Constant C may be chosen to optimize thesignal-to-noise ratio SNR in a particular system, and constant β in oneembodiment, may be 0.5. In certain embodiments, a transmitter maydetermine its transmission power to a specific receiver in the peerdiscovery and/or the paging phase of the communication. A transmittermay also update its transmission power by inspecting the recent controlchannel feedback from a specific receiver during a previoustransmission.

The first wireless terminal WT A 202 may transmit a traffic request 210to the second wireless terminal WT B 204. The second wireless terminalWT B 204 receives the traffic request 210 which may have a receivedpower Pr_(A)=P_(A)*h_(AB), where P_(A) is the transmit power of WT A 202and h_(AB) is the channel gain between WT A 202 and WT B 204, and whichcan also be represented as gain (WTA-WTB).

At the same time, the third wireless terminal WT C 206 may transmit atraffic request 214 to the fourth wireless terminal WT C 208 on the samecontrol channel as the traffic request from WT A to WT B. Because thetraffic request 214 is sent over a wireless medium on the same controlchannel, the second wireless terminal WT B 204 may also receive thetraffic request 214′ which may have a received powerPr_(C)=P_(C)*h_(BC), where P_(C) is the transmit power of WT C 206 andh_(BC) is the channel gain between WT C 206 and WT B 204, and which canalso be represented as gain (WTC-WTB).

If the ratio between the received power Pr_(C) (from WT C) and thereceived power Pr_(A) (from WT A) is greater than an acceptableinterference threshold (i.e., Pr_(C)/Pr_(A)>threshold), then the secondwireless terminal WT B 204 may yield the transmission channel to thirdwireless terminal WT C 206 by not sending an echo or reply transmissionto the first wireless terminal WT A 202. For instance, this may be thecase if the connection from WT C to WT D is higher priority than theconnection from WT A to WT B.

Otherwise, the second wireless terminal WT B 204 may reply to thereceived traffic request 210 with an echo transmission 212 having atransmit power P_(B) inversely proportional to the received power Pr(e.g., based on signal strength) received in the traffic request 210.For example, in one embodiment, the echo or reply transmission 212 fromWT B 204 is set to a transmit power P_(B)=C/(P_(A)*h_(AB)), where C=1.

Because a shared frequency spectrum (e.g., communication channel) isused by multiple wireless terminals for wireless transmissions over thenetwork 200, the third wireless terminal WT C 206 may also receive theecho or reply transmission 212′ from neighboring second wirelessterminal WT B 204. Although the echo transmission 212 is intended forthe first wireless terminal WT A 202, other neighboring wirelessterminals in the peer-to-peer network 200, including WT C 206, may alsoto receive the echo transmission 212′. Note that in someimplementations, the first wireless terminal WT A 202 and third wirelessterminal WT C 206 may utilize the same control and/or transmissionchannels (e.g., same frequency or timeslot) within the sharedcommunication channel or frequency spectrum. In other implementations,the first wireless terminal WT A 202 and third wireless terminal WT C206 may utilize different control and/or transmission channels withinthe shared communication channel but these different control and/ortransmission channels maybe sufficiently close that the energy fromtransmissions in one channel (for a first wireless terminal) interfereswith transmissions in another channel (for another wireless terminal).

At the third wireless terminal WT C 206, the received echo transmission212′ may have a received power P_(r)=h_(BC)/(P_(A)*h_(AB)), where P_(A)is the transmit power of WT A 202, h_(AB) is the channel gain between WTA 202 and WT B 204, and h_(BC) is the channel gain between WT B 204 andWT C 206, and which can also be represented as GAIN (WTC-WTB). Note thatit is the use of inversely proportional power in the echo transmissionthat allows the transmitting terminals to perform transmitter yieldingbased on the received echo transmissions.

The third wireless terminal WT C 206 may use the echo transmission 212′(and potentially other echo transmission for other wireless terminals)to ascertain whether it should transmit on a particular transmissionchannel (i.e., corresponding to the control channel being used) or allowa different terminal to use the transmission channel. That is, the thirdwireless terminal WT C 206 may use the echo transmission 212′ toascertain whether its own transmission (at a particular power Pc) mayadversely affect transmissions between WT A and WT B on the sametransmission channel. For example, upon receiving the echo transmission212′ from the second wireless terminal WT B 204, the third wirelessterminal WT C 206 may determine the signal noise to interference plusnoise ratio expected that may be perceived by the second wirelessterminal WT B 204 as:

$\begin{matrix}{\frac{h_{AB}P_{A}}{h_{BC}P_{C}} < {{SINR}.}} & \left( {{Equation}\mspace{20mu} 2} \right)\end{matrix}$where P_(C) is the proposed transmit power of the third wirelessterminal WT C 206 (which need not be fixed) and the SINR threshold is aparticular signal to interference plus noise ratio appropriate for thenetwork 200. The remaining terms of Equation 2 are derived from thereceived power (P_(r)) from the second wireless WT B 204. If Equation 2evaluates to true (i.e., SINR>(P_(A)*h_(AB))/(P_(C)*h_(BC))), then thethird wireless terminal WT C 206 determines that its transmission to WTD 208 (e.g., or any other wireless terminal in network 200 on the sametransmission channel as the transmission from WT A to WT B) wouldnegatively impact the transmission from the first wireless terminal WT A202 to the second wireless WT B 204. Therefore, the third wirelessterminal WT C 206 may yield transmission to WT A 202. However, ifEquation 2 evaluates to false (i.e.,SINR≦(P_(A)*h_(AB))/(P_(C)*h_(BC))), then the third wireless terminal WTC 206 determines that its transmission to WT D 208 (e.g., or any otherwireless terminal in network 200 on the same transmission channel as thetransmission from WT A to WT B) would not negatively impact thetransmission from WT A 202 to WT B 204. Therefore, the third wirelessterminal WT C 206 may proceed to transmitting on the same transmissionchannel as WT A 202.

According to one feature, the third wireless terminal WT C 206 may yieldtransmissions on a first transmission channel to the first wirelessterminal WT A 202 only when WT A 202 has higher priority than WT C 206.The priority for each transmitting wireless terminal can be based on aparticular priority scheme, such as priority based on its frequencyindex assignment, for example. In a priority-based arrangement, lowerpriority terminals or devices may yield to higher priority terminals ordevices.

Note that other wireless terminals perform the same receiver yieldingand transmitter yielding as described above. That is, this protocol maybe understood, established, and/or implemented throughout the network sothat other peer-to-peer transmitter/receiver devices also performtransmitter/receiver yielding. For example, the third wireless terminalWT C 206 may send a traffic request 215 at power P_(C) to the fourthwireless terminal WT D 208. The fourth wireless terminal WT D 208 mayperform receiver yielding if transmissions from WT C 206 are likely tointerfere with transmissions from WT A 202 to WT B 204. That is, thefourth wireless terminal WT D 208 may not send an echo transmission tothe third wireless terminal WT C 206, thereby declining the connectionand yielding to the connection between WT A 202 and WT B 204. Forinstance, WT D 208 may receive the traffic request 214 at powerP_(C)*h_(DC) (where h_(DC) is the channel gain between WT C and WT D)and the traffic request 210′ at power P_(A)*h_(AD) (where h_(AD) is thechannel gain between WT A and WT D). If (P_(C)*h_(DC))>(P_(A)*h_(AD))and the connection between WT A and WT B has a higher priority, thefourth wireless terminal WT D 208 may not send a reply echotransmission, thereby yielding the channel to the connection between WTA and WT B.

Thus, by implementing receiver yielding and/or transmitter yieldingamong the wireless terminals in a peer-to-peer network system,connection scheduling and prioritization may be achieved.

Channel Architecture

FIG. 3 illustrates one example of a transmission channel architecture300 that may be used by wireless terminals to transport controlsignaling and traffic for a peer-to-peer communication connectionbetween wireless terminals. One example of a channel architectureincludes a control slot 314 in inserted every so often between trafficslots 310. A peer-to-peer transmission channel 300 may include aplurality of traffic slots 310. Traffic slots 310 are time intervalsduring which a transmitter terminal may send peer-to-peer traffic datato a receiver terminal through the transmission channel.

Each traffic channel slot 310 may include a traffic management channel301 and a traffic channel 303. The traffic management channel 301 may beused for signaling related to traffic data transmissions in the trafficchannel 306. A connection scheduling segment 302, a rate schedulingsegment 304, and an acknowledgment segment 308 are collectively referredto as the traffic management channel 301. A data transmission segment306 may be referred to as the traffic channel 303. The connectionscheduling segment 302, the rate scheduling segment 304, the datasegment 306 and the acknowledgment 308 shown in FIG. 3 comprise atraffic slot.

The connection scheduling segment 302 may be used by a transmitterterminal to indicate to its receiver terminal (in a peer-to-peerconnection) to indicate that it is ready to transmit traffic data. Therate scheduling segment 304 allows the transmitter/receiver terminals(in the peer-to-peer connection) to obtain a transmission rate and/orpower to use in transmitting the traffic data. The data transmissionsegment 306 is then used to transmit the desired traffic data at theobtained transmission rate and/or power. The acknowledgement segment 308may be used by the receiver terminal to indicate that the traffic datawas received or not received in the data transmission segment 306. Inone example, the time duration of a traffic slot is approximately two(2) milliseconds. As the traffic slots 310 repeat over time, the timesequence structure shown in FIG. 3 shows one period of the trafficslots. Note that, prior to sending traffic data in the traffic slot 310,the transmitter and receiver terminals may have established apeer-to-peer connection via a control slot 304 (in FIG. 3).

In the connection scheduling stage 302, the first device WT A 202 (FIG.2) may transmit a first transmission request, which is heard by thesecond device WT B 204. The second device WT B 204 then transmits asecond transmission request response, which is heard by the first deviceWT A 202 so that the first device knows that the second device is readyto receive traffic transmission from the first device. Both the firstand the second devices WT A 202 and WT B 204 proceed to the secondstage. Meanwhile, the second transmission request response is also heardby the third device, which will determine whether it will cause largeenough interference to the second device if it chooses to proceed totransmit traffic channel. If it is determined that it will causeexcessive interference, the third device will choose not to proceed tothe second stage of the protocol. For the sake of description, it isassumed that the traffic transmission from the third device is of lowerscheduling priority.

In the rate scheduling stage 304, the first device WT A 202 transmits afirst pilot signal. If the third device WT C 206 does not drop out inthe connection scheduling stage, it also transmits a second pilotsignal. The second device WT B 204 determines a data rate it can supportof the traffic transmission from the first device WT A 202 as afunctional of the received signal strengths of the first pilot from thefirst device and the second pilot from the third device. The seconddevice WT B then sends a rate report to the first device WT A 202 whichincludes the determined data rate.

In the data or traffic transmission state 306, the first device WT A 202determines an actual data rate, as a function of the received ratereport from the second device WT B 204, and transmits traffic to thesecond device WT B 204.

The transmission channel 300 may also include a control channel 314comprising a plurality of control slots 314. A control slot 314 mayserve to establish and maintain a peer-to-peer connection between thetransmitter and receiver terminals. Each control slot 314 may include aSignaling Broadcast Channel 316 and a Paging Channel 318. The SignalingBroadcast Channel 316 may be used, for example, to indicate thosepeer-to-peer connection identifiers (CIDs) that are in use by nearbyconnections and to indicate whether a peer-to-peer connection is stillalive. For example, the transmitter and receiver terminals may monitorthe Signaling Broadcast Channel 316 to determine which CIDs are in use.The Paging Channel 318 is used by the transmitter and receiver terminalsto establish new CIDs for a new peer-to-peer connection. The controlslots 314 may occur at much longer intervals than traffic slots 310. Forinstance, the control slots 314 may occur every second or so.

FIG. 4 illustrates an example time-frequency grid 400 that may be usedin signal transmissions over the channel architecture of FIG. 3. Theexemplary signal may be an OFDM signal. The time-frequency grid 400 isthe resource available for transmitting and/or receiving signals over apeer-to-peer network, e.g., during a control slot (e.g., control slot314) and/or traffic channel slot (traffic slot 310 in FIG. 3 withintraffic management channel 301). The x-axis represents time and mayinclude N symbols (e.g., where N may be any integer), and the y-axisrepresents frequency and may include M tones (e.g., where M may be anyinteger).

A transmitter and/or receiver terminal may use the time-frequency grid400 in the traffic management channel. For instance, the time-frequencygrid may be considered a connection identifier CID resource space fromwhich a terminal may select a CID resource unit corresponding to a CID.For example, in a traffic slot, a transmitter terminal may select a CIDresource unit to signal a transmission request to the correspondingreceiver terminal of the connection associated with the CID. Similarly,the receiver terminal may select a CID resource unit to signal a requestresponse to the transmitter terminal. The CID resource units availablefor the transmitter terminal and for the receiver terminal may bepartitioned a priori in a fixed manner so that the transmitter terminalselects a CID resource unit in a fixed subset of the totaltime-frequency grid of the traffic management channel, while thereceiver terminal selects a CID resource unit in a different fixedsubset of the total time-frequency grid 400 of the traffic managementchannel. Such CID resource space may be transmitted, for example, in acontrol slot 314 and/or traffic slot 310 (e.g., within trafficmanagement channel 301).

A CID resource unit may be defined by a symbol-tone combination (e.g., asubset of tones within a symbol). According to an example, in a controlslot or a traffic management portion of a traffic slot, a terminal mayselect a particular symbol (e.g., transmission time) for transmissionbased upon an identifier of the wireless terminal or a user who isutilizing the wireless terminal and/or a time variable (e.g., timecounter) that may be commonly understood within a peer-to-peer networkto identify the current slot interval. Further, a particular tonecorresponding to the selected symbol may be determined (e.g., based uponthe identifier and/or time variable). Pursuant to a further example, ahash function of the identifier and the time variable may yield theselected symbol position and/or tone position. For example, for a givenpeer-to-peer connection, when the time variable takes a first value, thehash function may yield symbol x₁ and tone y₁ such that the wirelessterminal transmits a single-tone signal as the CID resource unit. Whenthe time variable takes a second value, the hash function may yieldsymbol x₂ and tone y₂ such that the wireless terminal transmits asingle-tone signal P₂ as the CID resource unit.

Interference Mitigation Protocol

In an ad hoc peer-to-peer communication system, multiple communicationsmay take place using frequency spectrum resources shared in both spaceand time. Because of the distributed nature of the ad hoc peer-to-peernetwork, it may not always be possible to control the channelallocations (e.g., slots) used for transmissions between the wirelessterminals. In wireless networks where a central authority does notexist, interference avoidance and/or management is a key feature tomaintain the efficiency of the network performance.

In general, for a first terminal to send traffic to a second terminalover a peer-to-peer connection, it first sends a traffic request signalin the traffic management channel 301 (FIG. 3). Upon receiving thetraffic request signal from the first terminal and possible trafficrequest signals from other terminals in the vicinity that intend to usethe same traffic slot as the first terminal, the second terminal maysend back a traffic request response signal, also in the trafficmanagement channel 301. It is also possible that the second terminaldoes not send back the traffic request response signal if it senses thatanother higher priority transmitter is also requesting use of thecurrent traffic slot. After the first terminal receives the trafficrequest signal from the second terminal and possibly other trafficrequest signals from other terminals in the peer-to-peer network, itwill make a decision on whether or not to use the current traffic slot.The decision is made by measuring the signal strength of the trafficrequest response signals from higher priority receiver terminals in thepeer-to-peer network. If any of the signals has strength above a certainthreshold, the first terminal thinks that it is creating a stronginterference for the corresponding higher priority receiver terminal andwill decide to refrain using the current transmit slot.

FIG. 5 is a flow diagram illustrating the operation of various wirelessterminals in an ad hoc peer-to-peer network that facilitates connectionscheduling where a plurality of wireless terminals share a communicationchannel. In this example, it is assumed that the shared communicationchannel includes a control channel and a transmission channel. A firstwireless terminal WT A 502 may select a transmit power P_(A) andtransmits a traffic request at power P_(A) 508 (or at a powerproportional to P_(A)) over the control channel to a second wirelessterminal WT B 504. Such traffic request may serve to establish apeer-to-peer connection between WT A 502 and WT B 504 over atransmission channel associated with the control channel. In thisexample, the channel gain between WT A 502 and WT B 504 is denoted byh_(AB). Upon receiving the traffic request 508, the second wirelessterminal WT B 504 may determine whether the received power(P_(A)*h_(AB)) of the traffic request is likely to interfere with anearby transmissions of higher priority and, if so, does not send anecho or reply transmission 509 to the first wireless terminal WT A. Forexample, WT B may estimate the signal to interference ratio, where thedesired signal power is (P_(A)*h_(AB)), while the interference power isdetermined by the received power of other traffic requests with higherpriority. Those traffic requests are sent by other transmitters to theircorresponding receivers. Otherwise, the second wireless terminal WT Bmay obtain a transmit power P_(B) that is proportional to1/(P_(A)*h_(AB)) 510. The second wireless terminal WT B 504 may thenbroadcast a reply or echo transmission at power P_(B) 512 (denoted 512 aor 512 b) in response to the traffic request from WT A. The firstwireless terminal 502 may then transmit to the second wireless terminalWT B 504 over the transmission channel 514 associated with the controlchannel.

Because the echo transmission 512 (denoted 512 a or 512 b) is broadcastover a shared communication channel, other nearby devices, such as thirdwireless terminal WT C 506, may receive the echo transmissions. If thethird wireless terminal WT C 506 is intending to use the samecommunication channel (or frequency spectrum) to transmit to otherdevices, it may cause unacceptable interference to the transmissionsbetween WT A and WT B. Here, it is assumed that the connection of WT Cis of lower priority than the connection between WT A and WT B in thepresent traffic slot. Thus, WT C may need to make sure its intendedtraffic transmission does not create excessive to the receiver device WTB. Therefore, the third wireless terminal WT C 506 may ascertain arelative measure between its transmission (P_(C)*h_(BC)) and thetransmission from WT A (P_(A)*h_(AB)), as received by the secondwireless terminal WT B, where P_(C) is the transmission power for thethird wireless terminal WT C. Since the power of the echo transmissionas received at the third wireless terminal WT C is proportional to thechannel gain h_(BC) and the echo transmission power P_(B) orh_(BC)/(P_(A)*h_(AB)), a ratio (P_(A)*h_(AB))/(P_(C)*h_(BC)) may beascertained. The third wireless terminal WT C 506 can use this ratio asan indicator of whether its transmissions may negatively impactreception of the transmissions from the first wireless terminal WT A 502to the second wireless terminal WT B 504. For instance, if the ratio(P_(A)*h_(AB))/(P_(C)*h_(BC)) is greater than a signal to interferenceplus noise ratio SINR threshold, then the third wireless terminal WT C506 may conclude that its transmissions will have an unacceptablynegative impact on the transmissions from WT A 502 to WT B 504 and yieldthe transmission channel to the first wireless terminal WT A 516.Otherwise, if the ratio (P_(A)*h_(AB))/(P_(C)*h_(BC)) is less than orequal the SINR threshold, it may transmit on the shared transmissionchannel (e.g., to WT B or another device) 518.

By having each wireless terminal in a peer-to-peer network follow theprocedures illustrated in FIGS. 3 and 4, excessive interference can beavoided since wireless terminals that may cause interference to higherpriority wireless terminals will not transmit over the sharedtransmission channel, allowing the higher priority wireless terminal(s)to use that transmission channel instead. Transmission priority for eachtransmitting wireless terminal may be based on a particular priorityscheme, such as priority based on its frequency index assignment, forexample. In a priority-based arrangement, lower priority terminals ordevices may yield to higher priority terminals or devices.

In addition to connection prioritizing and/or scheduling, a wirelessterminal may also adjust its transmit power to avoid causinginterference to nearby wireless terminals. In some implementations, awireless terminal may include a variable power transmitter and areceiver.

In some implementations, a transmit power is obtained by a wirelessterminal and used for communications over its control channel and thecorresponding transmission channel. Note that, in one example, the sametransmit power is used in the control channel and the traffic channel,thereby facilitating connection scheduling.

The transmit power may be determined in different ways. For instance,the transmit power may be a constant power P₀, or power controlled(e.g., power P₀ divided by channel gain h), or a function of power P₀and channel gain h (e.g., P₀/√h). Note that the channel gain h is avalue between zero (0) and one (1) (e.g., 0≦h≦1) and may be obtained bythe transmitter wireless terminal beforehand, for example, during pagingor discovery phases of establishing the peer-to-peer connection.

In a first scenario, a wireless terminal may transmit at constant powerP₀. However, under constant transmit power P₀ the wireless terminal maycreate more interference than necessary. This is because the constanttransmit power P₀ is typically selected for the longest communicationrange which is wasted in shorter range communications. Therefore, unlessa connection has the highest priority, use of constant power P₀ willcause frequent transmitter yielding and/or receiver yielding since itwill cause interference with other connections. Thus, a connection usingconstant transmit power P₀ may be active for very small periods of timescheduled since transmitter yielding and/or receiver yielding will causeother connection (e.g., those that cause less interference or havehigher priority) to be favored. Additionally, the use of a constanttransmit power is also wasteful of limited power resources oftenavailable to mobile or portable wireless terminals.

In a second scenario, a wireless terminal may transmit at a controlledpower P₀/h (taking into account channel gain h) so that the receivedpower is constant. Under this scenario, the power may be adjusted basedon channel gain. However, under this approach, the controlled transmitpower P₀/h may be lower than ideal, especially where the channel issusceptible to sporadic interference.

In a third scenario, a wireless terminal may transmit at a scaled powerP_(scaled)=P₀/f(h) (where f(h) is a function of channel gain h). Forinstance, the scaled transmit power P_(scaled) may be a predeterminedconstant power P₀, or a function of measured channel gain, e.g.,inversely proportional to channel gain C*P₀/h, or to the square root ofchannel gain D*(P₀/√h), where C and D may be different scaling factorsfor antenna gains (e.g., for receiver and/or transmitter antennas). Inone example, by adjusting transmit power relative to the constanttransmit power, the wireless terminal WT A 502 may reduce interferenceto other wireless terminals and, consequently, may have the opportunityto have transmissions scheduled more often.

FIG. 6 is a flow diagram illustrating how transmit power scaling may beimplemented for a peer-to-peer connection between two wirelessterminals. A first wireless terminal WT A 602 may obtain a channel gainh_(AB) 606 for the communication channel to a second wireless terminalWT B 604. The wireless terminal WT A 602 may obtain a scaled transmitpower P_(A) based on a constant power P₀ and a function f of the channelgain h_(AB) 608. For instance, in one example the transmit power may beP_(A)=P₀/square_root(h_(AB)).

Optionally, connection scheduling may be performed 607 for theconnection between the wireless terminals WT A 602 and WT B 604. Forexample, such connection scheduling may be performed according to atransmitter yielding and/or receiver yielding scheme as illustrated inFIGS. 3 and 4, and/or during the connection scheduling segment 302 ofFIG. 3.

The first wireless terminal WT A 602 may then transmit a pilot signal ata power C*P_(A) 610 to the second wireless terminal WT B 604. That is,the total pilot transmit power may have a fixed relationship with thetotal data transmit power of the corresponding data traffic segment. Forexample, depending on the signal format of the pilot signal, if thepilot is a single-tone signal while the data signal is spread acrossmany tones, then the per tone power may be higher for the pilot signalthan for the data signal.

The second wireless terminal WT B 604 may then obtain or select atransmission rate R_(AB) based on the received signal power P_(A)*h_(AB)612. This transmission rate R_(AB) is sent 614 to the first wirelessterminal WT A 602 which can then transmit on a shared transmissionchannel at power P_(A) and at the transmission rate R_(AB) 616.

Under the interference mitigation protocol described herein, there is arelationship between the power a first terminal uses to send trafficrequest signal to a second terminal and the power the first terminaluses to send the traffic data in the traffic slot. The relationshipbetween the two powers is universally well understood throughout thenetwork since the powers will directly affect the receiver yieldingdecisions made at the receiver terminals and may also affect thetransmitter yielding decisions at other transmitter terminals. In someexamples, the relationship is to enforce the transmit power of thetraffic request signal to be proportional to the transmit power of theactual traffic data transmission, where the ratio between the two may beconstant and known to all the terminals in the network. In one example,the constant is equal to 1.

However, there may be reasons that the transmitter terminal may want toadjust the above power ratio. In one example, the transmitter terminalmay want to reduce the transmission power of the traffic slot, so thatit would cause less interference to other high priority traffictransmissions—this way, the transmitter terminal may not have to TXyield to those high priority traffic transmissions. In another example,if the transmitter terminal does not have much data to send, using largetransmission power in the traffic block is wasteful. In the aboveexamples, it is desired that the transmitter terminal reduces thetraffic transmission power. For example, suppose that the transmitterterminal transmits the traffic signal in the entire traffic slot. Whenthe transmitter terminal reduces the transmission power, although thetransmission power per degree of freedom (e.g., per tone in an OFDMsymbol) is reduced, the transmitter terminal can use a low coding rateto compensate the reduced SNR per degree of freedom and thereforemaintain the proper Eb/N0 requirement. In effect, the transmitterterminal adjusts the coding rate, and therefore the amount of data to betransported in the data block, in order to accommodate the reduction intransmission power.

Overview of Small Packet Transmissions in Peer-to-Peer Network

In some instances, a device may wish to transmit a small amount of datathat is smaller than a normal traffic frame size or length.Consequently, the small amount of data can be transmitted in a “smallpacket” rather than a normal traffic frame. As used herein, a “smallpacket” may include a packet or amount of data that is smaller than amaximum threshold length. Such “small packet” has a length that issmaller, by a pre-determined amount, than a normal frame length. Forinstance, the small packet may have a length or size that is smaller byfifty percent or smaller than the normal frame size. In other example, atypical frame size may be 4000 bits long and a small packet is 1000 bitsor less.

When transmitting a small packet, a transmitter intends to use lesstraffic transmission power than when transmitting a normal packet, sothat the small packet traffic transmission causes less interference toother traffic transmissions in the vicinity. The reason that thetransmitter is able to reduce transmission power without scarifyingcommunication reliability is that the transmitter may use low codingrate to maintain the required Eb/N0. However, the corresponding controlinformation, e.g., transmission request, may need to be transmitted atthe same power as it would have had the transmission been a normal orlarge packet transmission. This is because the same amount of controlinformation needs to be communicated irrespective of whether traffic isa small or normal packet. Under normal receiver yielding, a receiverdevice may seek to reduce a transmitter device's traffic transmissionpower to minimize interference to other nearby device. However, under analternative approach, if the transmitter device knows that it is goingto send a small packet, it can signal this intent to the receiver deviceby using a separate bit. This bit for example can be transmitted usingposition based coding. This bit indicator means that the transmitterdevice will transmit the small packet at a lower power than other typesof transmissions, without the need for the receiver terminal to indicatea lower power via receiver yielding.

A rate prediction algorithm can be split into a channel measurementstage and an interference measurement stage. A small packet transmitterdevice uses the full power for the channel measurement stage whereas ituses a reduced power for the interference measurement stage. This hasthe advantage of providing a good channel estimate, since thetransmitter device used the full power, without compromising on theinterference measurement since the transmitter used the reduced power inthe interference measurement part that will also be used for the datatransmission.

In addition to lowering the transmit power by a fixed amount, additionalpower back off for the transmitter device can be signaled by thereceiver device in a rate feedback stage. For a small packettransmission, the rate granularity required would in general be muchsmaller than the normal or large packet transmission. The fact that thetransmission is a small packet transmission has already beencommunicated to the receiver device during the rate scheduling stage.Therefore, the remaining bits in the rate feedback can be used toindicate to the intended transmitter device to further reduce the powerof the transmission. This may not improve the rates for other nearbydevices, but may reduce the interference caused to the other receiverdevices and also increases the battery life of the transmitter device.

Transmit Power Backoff for Small Packet Transmission

According to a first scheme, the transmitter power is reduced since asmaller packet will require much lower SNR. This will maintain theE_b/N_(—)0 for the transmission as well as minimize the interferencecaused to other wireless communications happening in the same spectrum.

The fact that the transmitter power is reduced for a small packet can besignaled in a control channel so that other nearby devices can use thisinformation for their scheduling and rate prediction algorithms. As inthe baseline protocol described in FIGS. 3 and 4, three stages may beemployed.

FIG. 7 illustrates an example of how power may be reduced whentransmitting a small packet in a peer-to-peer network. In this example,a first device WT A 702 has a peer-to-peer connection with a seconddevice WT B 704 while a third device WT C 706 has a peer-to-peerconnection with a fourth device WT D 708. Since the devices operatewithin range of each other in a shared frequency spectrum, transmissionsfrom the third device WT C 706 to the fourth device WT D 708 areconsidered “interfering” to transmissions from the first device WT A 702to the second device WT B 704. In this example, the first device WT A702 intends to transmit a small packet to the second device WT B 704over their peer-to-peer connection. Such small packet size or length maybe an amount of data that is smaller than a threshold size or datalength.

The first device WT A 702 first determines whether the data traffic tobe transmitted in the current time slot is “small” (e.g., smaller than acertain threshold size) or not and select either a small packet ornormal packet indicator depending on size of data traffic to be sent711.

During a connection scheduling stage 710, the first device WT A 702 usesthe same first power level in the transmit request resource as it doesfor any other normal size or length packet transmission. That is, thefirst device WT A sends a first transmission request to the seconddevice WT B at the first power level along with a packet size indicator712. Such indicator may be a single bit, or one or two phases thatindicates either a normal or small packet. In another example, thetransmitter device may have two tones to signal the traffic request, inwhich case the transmitter may use a first tone to send a referencesymbol and a second tone to signal information related to whether thecorresponding traffic is a small or normal packet, and if it is a smallpacket, how much power backoff (i.e., power reduction) the transmitterwill use in the traffic signal relative to the power used for a normalpacket traffic. In one embodiment, the information is signaled in thephase of the second tone. For example, the phase of the second tone canbe discrete QPSK, where 00 (phase=0 degree) represents a normal packet,01, 10, 11 (phase=90, 180, 270 degrees), all represent a small packetwith different power backoff values. In another example, the phase ofthe second tone may not be discrete. For example, phase=0 degreerepresents a normal packet, while phase is anywhere from 90 to 270degree representing a small packet traffic. Phase=90 or 270 degreerepresent a minimum or maximum value of power backoff. The phase valuein between 90 and 270 degrees represents a power backoff value betweenthe minimum and the maximum values. This way, the phase can be used tosignal much more possible power backoff values. In a correspondingtransmit response resource, the second device WT B 704 echoes therequest response using the same second power level as it uses for normalsize or length packet transmission. That is, the second device WT Bsends a first transmission request response to the first device WT A atthe normal second power level 714. Note that, in one example, the secondpower level may be inversely proportional to the first power level. Itis desirable, though not required, for the small packet transmitterfirst device WT A 702 to also indicate the nature of the transmission bymarking one bit in transmit request message.

For the transmitter yielding decision 717, the transmitter devices WT A702 and WT C 806 operate as discussed under the baseline protocol. Forinstance, the lower priority third device WT C 706 may detect therequest response 714 b and determine whether its own data traffictransmission in the same traffic slot will cause unacceptableinterference to the second device WT B 704. For example, since therequest response 714 is inversely proportional to the transmit power ofthe first device WT A 702, the third device WT C 706 knows whether itsown transmit power will cause unacceptable interference to the seconddevice WT B 704.

For the receiver yielding decision 716, the receiver devices WT B 704and WT D 708 have to first decide the nature of the interferingtransmissions, if available, and take that into account in making theyielding decision. For example, the receiver fourth device WT D 708 maysense a higher priority transmitter WT A 702 with strong received powerin the request signal but it also finds out that the transmission (fromWT A to WT B) is a small packet transmission. The fourth device WT D 708can find this out because this information is included in the firsttransmission request. In this case, the fourth device WT D 708 might nothave to yield since the traffic transmission power of the transmitter WTA 702 will be much smaller than the first power level it used in theconnection scheduling stage 710. Furthermore, when the transmitter WT A702 indicates the amount of power backoff, the fourth device WT D 708can predict the interference power caused by the traffic signal from WTA by using the measurement from the traffic request signal 712 and thedecoded power backoff. For example, if the measured power of thereceived traffic request signal is X and the power backoff announced byWT A is Y, then the predicted interference power may be X/Y. Forexample, if Y is 10 dB, then the predicted interference power is 10times smaller than the measured power of the received traffic requestsignal.

In the above discussion, it is assumed that WT C to WT D traffic is oflower priority than WT A to WT B traffic so that WT D needs to considerthe receiver yielding. In another scenario where WT A to WT B traffic isof lower priority than WT C to WT D traffic, WT A needs to consider thetransmitter yielding. For example, the transmitter device WT A 702 maysense a higher priority receiver WT D 708 with strong received power inthe request response signal but it also knows that the transmission(from WT A to WT B) is a small packet transmission. In this case, WT A702 might not have to yield since the traffic transmission power of thetransmitter WT A 702 will be much smaller than the first power level itused in the connection scheduling stage 710 so that WT A may not causeas much as interference to WT D. For example, if the power backoff usedby WT A is 10 dB, then the interference from WT A to WT D is ten (10)times smaller when WT A is going to transmit a small packet traffic thanwhen WT A is going to transmit a normal packet traffic.

For the rate scheduling stage 718, the rate prediction algorithm issplit in two parts: first a channel measurement part, and second aninterference measurement part. The small packet transmitter first deviceWT A 702 uses the full power for the channel measurement part but usesthe reduced power for the interference measurement part. This has theadvantage of providing a good channel estimate, since the transmitterfirst device WT A used the full power, without compromising theinterference measurement since the transmitter WT A 702 used the reducedpower in the interference measurement part that will also be used forthe data transmission.

In the rate feedback of this stage, pilot signals 720 and 722 arebroadcast by the transmitter first device WT A 702 and third device WT C706. The second device WT B 704 can utilize the signal strength of thereceived pilots to generate a first maximum rate for traffictransmissions 724 from the first device WT A 702. This first maximumrate is provided 726 to the first device WT A 702. Additional power backoff for the transmitter device WT A 702 can also be signaled by thereceiver device WT B 704, since now the second device WT B 704 has amore precise estimation of the channel condition. For a small packettransmission, the rate granularity required would in general be muchsmaller than the large packet transmission. And the fact that thetransmission is a small packet transmission has already beencommunicated to the receiver during the connection scheduling stage.Therefore, remaining bits in the rate feedback can be used to indicateto the intended transmitter to further reduce the power of thetransmission. This will not improve the rates for other devices, butwill reduce the interference caused to other devices and also increasethe battery life of the device.

Flash Signaling for Small Packet Transmission

According to one example, flash signaling (non-Gaussian) may be used totransmit small packets over the data burst of a large size. That is, anindication of a packet size may be provided by using one of eitherGaussian signaling or flash signaling. In the connection schedulingstage, one option is to let the small-packet transmitter WT A indicateits intention to transmit a flash signaling packet by marking one bit inthe transmit request message. The small packet receiver WT B monitorsthe transmit request resource and echoes a transmit request response,which also carries the information of the nature of the grantedtransmission.

A set of preferable rules for making transmitter and receiver yieldingdecisions may be defined among devices.

First, for receiver yielding decision at small packet receivers, adifferent threshold is used on the received power in the transmitrequest resource for making yielding decision to interfering normaltransmission as compared to the threshold used to receive a normal sizepacket transmission. For receiver yielding decisions at normal packetreceivers, the baseline protocol (described in FIGS. 2, 3, 5, and 6) isused to make yielding decision against other interfering normal packettransmissions. However, the normal packet receiver uses a differentthreshold to decide whether to yield to a higher priority interferingflash transmission. The threshold is chosen such that the flashtransmission does not desense the reception from its intendedtransmitter. In addition, the yielding decision can also take intoaccount of the loss of degrees of freedom due to the presence of higherpriority flash signaling devices.

Second, for transmitter yielding decision against other interferingflash signaling transmissions with higher priority should be related tothe number of such interfering transmissions with higher priority. Thisis because the decoding performance of flash signaling is vulnerablewhen coexisting with too many other flash signaling devices. Fortransmitter yielding decision at a small packet transmitter, thetransmitter monitors the request responses in the transmission requestresponse resource. Similarly, the transmitter uses a different powerthreshold to decide whether to yield to an interfering normal packettransmission as compared to the threshold it would use if thetransmission is for a normal packet. More precisely, the yieldingdecision is made when the flash signaling transmitter realizes that itmight desense a higher priority normal packet transmission. Fortransmitter yielding decision at normal packet transmitter, thetransmitter uses the baseline protocol (described in FIGS. 2, 3, 5, and6) to decide whether to yield to another normal packet transmission. Itwill use a different threshold to decide whether to yield to a smallpacket transmission.

Another choice for the connection scheduling is to use the samesignaling as in the baseline protocol (described in FIGS. 2, 3, 5, and6) for both small packet and normal packet transmissions. However, forthe small packet transmitter, the transmitter device monitors thetransmission request response resource and makes a decision then aboutwhether to use flash signaling or not. A small packet transmitter mightdecide to use flash signaling if all or part of the following conditionsare satisfied:

-   -   A. The number of bits contained in the current packet can be        transmitted using flash signaling (e.g., the data traffic packet        is smaller than a threshold size).    -   B. A normal transmission is not allowed, e.g., the transmitter        would have to yield to other higher priority transmissions if        the baseline protocol is used.    -   C. The flash signaling transmission would not desense any other        higher priority transmissions.

In the rate scheduling stage, if the flash signaling decision is made atthe end of the connection scheduling stage, it is necessary for thetransmitter to indicate its intention to use flash signaling here. Aneasy way to do this is for the transmitter to use a different pilotscheme other than the pilot scheme used by normal packet transmissions.For example, a normal packet transmission can use pseudo-random noise(PN)-like pilot signal in rate scheduling stage while a flash signalingformat can use beacon-type pilots. The intended receiver has to make abinary hypothesis testing to check the format of the data transmission.However, the total power to be used on the pilots are the same for bothpilot formats so that other coexisting receivers can still get a goodestimate of the interference caused by the flash signaling transmitter.

In the traffic transmission stage, the small packet transmitter, ifdeciding to use Flash signaling transmission, will only put power on asubset of the degrees of freedom in the current data burst. The datainformation will be carried over the position of these degrees offreedom only or a combination of position and phase difference. To usethe phase information, part of the degrees of freedom used in flashsignaling will serve as pilots for the total transmission. When such ascheme is used, a small packet can transmit around 400-600 bits over adata burst of 6000 degrees of freedom without causing much disturbanceto the neighboring normal transmissions, i.e., the other transmissionswill take the degrees of freedom used by flash signaling as erasures,which can be recovered from coding.

Flash Signaling and Detection

In flash signaling, there are some techniques that can be used toimprove the performance when the interference is from other flashsignaling users. To describe these techniques, a typical non-Gaussiansignaling scheme is outlined. Consider a data segment with 6400 degreesof freedom. It is divided into 100 disjoint segments of size 64 each.Now the transmitter modulates 6 coded bits onto one segment usingposition coding (6=log 2(64)). That is, the transmitter will send highenergy on a tone corresponding to the 6 coded bits. Thus, this schemeprovides a way to send 6*100 coded bits. These coded bits for examplecan be generated from an inner code of dimension (600, 400). Thereceiver makes hard/soft decisions for each segment to determine the 6coded bits that were sent, and then feeds this information to a decoderfor the inner code. A good choice for the inner code is a Reed-Solomoncode.

Now, consider the scenario in which a first device WT A is sending asmall packet to a second device WT B using non-Gaussian signaling, and athird device WT C is sending a small packet to a fourth device WT Dusing non-Gaussian signaling. So, the signal from third device WT C actsas interference to the second device WT B. Thus, second device WT B istypically going to receive two high-energy tones in each segment and ithas to decide which tone was sent by first device WT A and which tone isthe interference sent by the third device WT C. In one example, thephase of the signal can be used to make this distinction. Note that theposition/power is being used to convey the information, hence theremaining dimension, phase, can be used to deal with the interference.Note that in this scenario, the behaviors of the first device WT A andthird device WT C are similar and that of the second device B and thefourth device D are similar.

For interference management, three schemes are proposed.

Scheme 1:

A first device WT A sends a high energy tone at a fixed power (P1) and afixed phase (theta1) for all segments. Thus, the signal S1 received forthe high energy tone at the second device WT B isS1=sqrt(P1)*exp(j*theta1). Similarly, I3 may be the interference thatthe second device WT B receives from the third device C. The complexnumbers S1 and I3 are known to the second device WT B which can be done,for example, through the pilot control channel or connection schedulingchannel or a combination of both. The second device WT B then uses S1and I3 to determine the high energy tone that was sent by the firstdevice WT A. The idea is that the received signal should have highenergy, and be closer to S1, but not close to I3. Three canonical rulescan be used by the second device WT B for this purpose.

First, for each segment, determine the tone where the received signal isclosest in the Euclidean distance sense to S1, and declare that as thetransmitted signal. That is, tone t that is:argmax∥y(t)−S1∥^2  (Rule 1)t=1, . . . , 64

Second, for each segment, determine the tone t that isArgmax∥y(t)∥^2−∥y(t)−S1∥^2  (Rule 1)

t=1, . . . , 64

Third, for each segment, determine the tone t1 that isargmax∥y(t)∥^2−∥y(t)−S1−I3∥^2 if t1=t2=t∥y(t1)∥^2−∥y(t1)−S1∥^2+∥y(t2)∥^2−∥y(t2)−I3∥^2 o/w  (Rule 3)

t1=1, . . . , 64

t2=1, . . . , 64

Note that Rule 1, and Rule 2 do not use I3, where as Rule 3 which is ageneralization of Rule 2 uses I3 and hence performs better, but is morecomplicated to evaluate.

Scheme 2:

The first device WT A sends the high energy tone at a fixed power (P1),but a phase (theta1(s)) that is changing pseudo-randomly with segment s.Thus, the signal received for the high energy tone at the second deviceWT B for segment s is S1(s)=sqrt(P1)*exp(j*theta1(s)). Similarly I3(s)is the interference that the second device WT B receives from the thirddevice WT C. The complex numbers S1(s) and I3(s) are known to the seconddevice WT B for each segment which can be done, for example, through thepilot control channel/link scheduling or a combination of both. Thesecond device WT B then uses S1(s) and I3(s) to determine the highenergy tone that was sent by first device WT A. The idea is that thereceived signal should be have high energy, and be closer to S1(s), butnot close to I3(s). Three canonical rules can be used by the seconddevice WT B for this purpose.

Rule 1—For each segment, s, determine the tone where the received signalis closest in the Euclidean distance sense to S1, and declare that asthe transmitted signal.argmax∥y(t)∥−S1(s)∥^2t=1, . . . , 64Rule 2—For each segment, s, determine the tone t that isargmax∥y(t)∥^2−∥y(t)−S1(s)∥^2t=1, . . . , 64Rule 3—For each segment, s, determine the tone t1 that isargmax∥y(t)∥^2−∥y(t)−S1(s)−I3(s)∥^2 if t1=t2=t∥y(t1)∥^2−∥y(t1)−S1(s)∥^2+∥y(t2)∥^2−∥y(t2)−I3(s)∥^2 o/wt1=1, . . . , 64t2=1, . . . , 64A good choice for the pseudo-random variation theta1(s) is that it isindependent across segments and uniform between 0 and 2*pi for eachsegment.Scheme 3:

Scheme 3 is very similar to scheme 2, but both power and phase changepseudo-randomly with the segment. That is, the first device WT A sendsthe high energy tone at a power (P1(s)) and phase (theta1(s)) that arechanging pseudo-randomly with segment s. Thus, the signal received forthe high energy tone at the second device WT B for segment s isS1(s)=sqrt(P1(s))*exp(j*theta1(s)). Similarly I3(s) be the interferencethat the second device WT B receives from the third device WT C. Thecomplex numbers S1(s) and I3(s) are known to the second device WT B foreach segment which can be done, for example, through the pilot controlchannel/link scheduling or a combination of both. The second device WT Bthen uses S1(s) and I3(s) to determine the high energy tone that wassent by the first device WT A. The idea is that the received signalshould be have high energy, and be closer to S1(s), but not close toI3(s). The canonical rules that the second device WT B uses are the sameas that of scheme 2.

A good choice for the pseudo-random variation theta1(s) is that it isindependent across segments and uniform between 0 and 2*pi for eachsegment, and a good rule for the pseudo-random variation P1(s) is thatthe lowest value that it takes be lower bounded by 10 db overinterference. This is so that the tone does not get confused with thebackground Gaussian interference.

A flash signaling receiver first estimates the phase rotation from itsintended transmitter in the rate scheduling phase of the protocol andthen uses the estimated phase rotation in addition to received powerlevel to determine the set of tone-symbols (degrees of freedom) used byits Flash transmitter in the data transmission segment.

A flash signaling transmitter first determines a subset of tone-symbols(or degrees of freedom) in the data transmission block based on thecodeword to be transmitted. The information is coded by the position ofthese tone-symbols.

In addition, the transmitter may apply phase rotation pattern to thesignals to be transmitted over the chosen tone-symbols where said phaserotation pattern is a based on the identity of the transmitter, which isknown by its receiver.

FIG. 8 illustrates a method operational at a second device having apeer-to-peer connection with a first device to facilitate interferencemanagement of small packet transmissions using flash signaling within anad hoc wireless network. The second device receives a signal in aplurality of predetermined subsets of resource units 802. Calculate afirst phase to be used in a desired signal in each of the plurality ofpredetermined subsets of resource units, the desired signal being sentby a desired device 804. Note that the calculation of the first phase isnot based on the received signal but based on the expected format of thedesired signal. The expected format may be determined by the identifiersof the connection, the transmitter and/or receiver. Determine oneresource unit in each of the plurality of predetermined subsets ofresource units in which the desired signal is sent as a function of thereceived signal and calculated first phase 806. To do so, the seconddevice may use the rules described in the above.

The second device may further recover information bits transported inthe desired signal from the location of the determined one resource unitin each of the plurality of predetermined subsets of resource units 808.The calculated first phase may be the same in each of the plurality ofpredetermined subsets of resource units and is generated from at leastone of a first identifier associated with the first device, a secondidentifier associated with the second device and the peer-to-peerconnection between the first and second devices. The calculated firstphase may be determined as a function of a predetermined sequence, thecalculated first phase being different in different ones of thepredetermined subsets of resource units. The predetermined sequence maybe generated from at least one of a first identifier associated with thefirst device, a second identifier associated with the second device andthe peer-to-peer connection between the first and second devices.

The second device may also calculate a power to be used in the desiredsignal in each of the plurality of predetermined subsets of resourceunits, wherein the calculated power is determined as a function of apredetermined sequence, where the calculated power is different indifferent predetermined subsets of resource units, and the one resourceunit is also determined as a function of the calculated power 810. Thesecond device may also calculate a second phase to be used in aninterference signal in each of the plurality of predetermined subsets ofresource units, the interference signal being transmitted by aninterfering device, wherein the one resource unit is also determined asa function of the calculated second phase 812.

FIG. 9 illustrates a method operational at a first device having apeer-to-peer connection with a second device to facilitate interferencemanagement of small packet transmissions within an ad hoc wirelessnetwork. The first device may partition a set of resource units into aplurality of predetermined subsets of resource units 902 and thendetermines one resource unit in each of the plurality of predeterminedsubsets of resource units as a function of a set of bits 904. In anexample described previously, the set of resource units are partitionedinto 100 subsets, each of which having 64 resource units. Then for eachsubset, the first device determines one of the 64 resource units to senda signal, and the choice depends on the 6 bits to be signaled in thesubset. So totally 600 bits can be signaled using the 100 subsets. Theset of 600 bits may be generated from a set of information bits with anencoder. A signal is then transmitted by the first device in thedetermined one resource unit in each of the plurality of predeterminedsubsets of resource units 906. The phase of the transmitted signal inthe determined one resource unit is the same in each of the plurality ofpredetermined subsets of resource units and is generated from at leastone of a first identifier associated with the first device, a secondidentifier associated with the second device and the peer-to-peerconnection between the first and second devices.

The first device may further generate a plurality of phases as afunction of a predetermined sequence, where the phase of the transmittedsignal in the determined one resource unit in each of the plurality ofpredetermined subsets of resource units is equal to one of the generatedplurality of phases 908. The predetermined sequence may be generatedfrom at least one of a first identifier associated with the firstdevice, a second identifier associated with the second device and thepeer-to-peer connection between the first and second devices.

The first device may also generates a plurality of power values as afunction of a predetermined sequence, wherein the power of thetransmitted signal in the determined one resource unit in each of theplurality of predetermined subsets of resource units is equal to one ofthe generated plurality of power values 910.

Use Low Power in Traffic for Small Packet Transmission and Normal Powerin Connection Scheduling: (from a Transmitter's Perspective)

Under typical operation, a transmission request may have a firsttransmit power which is indicative of the transmit power of a subsequenttraffic signal. For example, the power used for the transmission requestsignal may be the same power as is subsequently used to transmit atraffic signal in a corresponding traffic slot. However, for smallpacket transmissions, a transmitter first device WT A may use the firstpower for the transmission request to a second device WT B but utilizesa lower second power for the small packet traffic transmissions.

It should be pointed out that because the transmitter first device maynot have much flexibility to adjust the coding rate used in thetransmission request signal, the transmission power in the requestsignal may not be reduced proportionally if it is determined that thetraffic transmission power is to be reduced. Otherwise, the transmissionrequest signal would be less reliable.

According to one feature, a transmitter first device may determine thetransmission power to send traffic data in a current traffic slot whenthe transmission request signal is sent so that other neighboringdevices in the peer-to-peer network can use the measurement from thetransmission request signal in order to properly predict and manage theinterference in the traffic slot. The transmitter first device maydetermine a power ratio between the traffic signal and the transmissionrequest signal, and further broadcasts the determined power ratio, e.g.,in the transmission request signal. In one example, the power ratio maybe one of two predetermined values. The transmitter first device maychoose one of the two values, and broadcasts the choice in thetransmission request signal (e.g., using 1 bit). The transmission powerused in the transmission request signal remains the same. When adifferent power ratio is used, the traffic transmission power is ineffect changed. For example, when the transmitter terminal does not havemuch data traffic to send in the traffic data block (i.e., a smallpacket mode), it chooses a power ratio so that the traffic transmissionpower is much smaller than when the transmitter terminal does have muchdata traffic to send (i.e., a normal packet mode). In one example, thedifference between the two power ratios is at least 10 dB. In otherwords, the power ratio can be one of a predetermined set of discretevalues. In yet another example, the power ratio can be any value betweenthe predetermined minimum and maximum values, in which case the possiblevalue of the power ratio is not discrete but continuous.

When the receiver second device recovers the specific power ratio to beused from the received request signal, the receiver second devicepredicts the received power of traffic transmission from the power ratioand the measured power of the received transmission request signal. Thereceiver second device then predicts the signal-to-interference ratio ofthe traffic transmission to determine whether it is ready to receivetraffic transmission from the transmitter first device. If so, thereceiver second device sends a request response signal to inform thetransmitter first device. The transmission power of the request responsesignal is determined as a function of the received power of thetransmission request signal. For example, the transmission power of therequest response signal is inversely proportional to the received powerof the transmission request signal.

In accordance with one aspect, the power of the request response signalmay be independent of the power ratio. In other words, even if thereceiver second device notices from the received power ratio informationin the request signal that the transmitter first device is going toreduce the traffic transmission power, the receiver second device doesnot increase or decrease the transmission power of the request responsesignal.

In one example, a first device WT A sends a first transmission requestsignal with a first power level to a second device WT B in a firsttransmission request resource associated with a first traffic slot. Thetransmission request signal may include a first packet lengthinformation for a first packet to be transmitted in the current trafficslot. The first device WT A then sends a first traffic signal includingthe first packet over the first traffic slot with a second power level.The first device may also send a second transmission request signal withthe first power level to the second device in a second transmissionrequest resource associated with a second traffic slot. The secondtransmission request signal including a second packet lengthinformation, where the second packet length information is differentfrom first packet length information. The first device then sends asecond data transmission signal over the second data transmissionresource with a third power level, where the third power level is atleast 3 dB smaller than the first power level.

There may instances where the transmitter first device may wish toadjust its announced power ratio of transmission requests signal powerto traffic signal power. In one example, the transmitter first devicemay want to reduce the transmission power of the traffic slot, so thatit causes less interference to other high priority traffic transmission.This way, the transmitter first device may not have to performtransmitter yielding to favor other higher priority traffictransmissions. In another example, if the transmitter first device maynot have much data to send, and using large transmission power in thecurrent traffic slot is wasteful. In the above examples, it is desiredthat the transmitter first device reduces the traffic transmissionpower. For example, suppose that the transmitter first device transmitsthe traffic signal in the entire traffic slot. When the transmitterfirst device reduces the transmission power, although the transmissionpower per degree of freedom (e.g., per tone in an OFDM symbol) isreduced, the transmitter first device can use a low coding rate tocompensate the reduced SNR per degree of freedom and therefore maintainthe proper Eb/N0 requirement. In effect, the transmitter first deviceadjusts the coding rate, and therefore the amount of data to betransported in the traffic slot, in order to accommodate the reductionin transmission power.

FIG. 10 (comprising FIGS. 10A and 10B) illustrates a method of operatinga first wireless device in a peer-to-peer communication network. Thefirst wireless device having a connection with a second wireless device.The first device may select a first power ratio value from a pluralityof predetermined power ratio values 1002. A first transmission requestsignal is sent by the first device in a first traffic slot 1004. Thefirst device then monitors (e.g., the first traffic slot) to receive arequest response signal from the second wireless device, the requestresponse signal indicating that the second wireless device is ready toreceive a traffic signal from the first wireless device 1006. If therequest response signal is received, the first device may send a firsttraffic signal in the first traffic slot with the transmission powerdetermined as a function of the transmission power of the firsttransmission request signal and the determined first power ratio value1014. Prior to sending the first traffic signal, the first device maysend a first pilot signal in a first part of a pilot channel associatedwith the first traffic slot, where the transmission power of the firstpilot signal being a function of the transmission power of the firsttransmission request signal 1008. Similarly, the first device may send asecond pilot signal in a second part of the pilot channel thetransmission power of the first pilot signal being a function of thetransmission power of the first traffic signal 1010. The first devicethen monitors (e.g., the current traffic slot) to receive a ratefeedback signal in a rate feed back channel associated with the firsttraffic slot, and wherein the transmission power of the first trafficsignal is determined also as a function of the rate feedback signal1012.

The ratio of the power of the first traffic signal and the power of thefirst transmission request signal may be equal to the determined firstpower ratio value. The first transmission request signal may includeinformation (e.g., such as a rate bit) indicative of the determinedfirst power ratio value. In one example, the first power ratio value isselected from two predetermined power ratio values, where the differencebetween the two predetermined power ratio values is at least 10 dB. Thefirst power ratio value may be determined as a function of the amount ofdata to be sent in the first traffic signal. According to one aspect,the first request signal may be sent in two tones and the informationindicative of the determined first power ratio value is signaled in aphase difference between the two tones. In one instance, the pluralityof predetermined power ratio values may include values in a continuousinterval between two predetermined values.

Subsequently, the first device may also check an amount of traffic datato be sent to the second wireless device 1016. A second power ratiovalue may be selected by the first device, as a function of the amountof data to be sent, from the plurality of predetermined power ratiovalues, where the second power ratio value is different from the firstpower ratio value 1018. A second transmission request signal is thensent in a second traffic slot 1020. The first device may then monitor toreceive a request response signal from the second wireless device, wherethe request response signal indicates that the second wireless device isready to receive a traffic signal from the first wireless device 1022.If the request response signal is received, the first device sends asecond traffic signal in the second traffic slot with the transmissionpower determined as a function of the transmission power of the secondtransmission request signal and the determined second power ratio value1024. The amount of data to be sent in the second traffic slot may be atleast twice as much as the amount of data sent in the first traffic slotand the second power ratio is at least 10 dB greater than the firstpower ratio. The transmission power of the second request signal may bethe same as the transmission power used in the first request signal.

FIG. 11 illustrates a method of operating a second wireless device in apeer to peer communication network. The second wireless device having aconnection with a first wireless device. In this example, the seconddevice may be a target of traffic transmissions from the first deviceover a peer-to-peer connection. A transmission request signal isreceived from the first wireless device, the first transmission requestsignal indicating that the first wireless device intends to send atraffic signal to the second wireless device and including informationindicative of a power ratio value 1102. The second device may recoverthe power ratio value from the transmission request signal 1104. Thepower of the received transmission request signal may then be measuredby the second device 1106. The power of the traffic signal to bereceived from the first wireless device may be predicted by the seconddevice as a function of the measured power of the received transmissionrequest signal and the recovered power ratio value 1108. The seconddevice may then determine whether to receive the traffic signal from thefirst wireless device as a function of the predicted power 1110. Thesecond device then sends a request response signal to the first wirelessdevice if it is determined to receive the traffic signal 1112. Thepredicted power may be equal to the measured power of the receivedtransmission request signal multiplied by the recovered power ratiovalue. The transmission power of the request response signal may bedetermined as a function of the measured power of the receivedtransmission request signal and may be independent of the recoveredpower ratio value.

FIG. 12 illustrates a method of operating a third wireless device in apeer to peer communication network. The third wireless device may have apeer-to-peer connection with a fourth wireless device. In this example,the third device is considered the interferer of peer-to-peercommunications between a first and second device having higher priority.The third device may receive a first transmission request signal in atraffic slot from the fourth wireless device, the first transmissionrequest signal indicating that the fourth wireless device intends tosend a traffic signal to the third wireless device 1202. The thirddevice receives a second transmission request signal in the traffic slotfrom a first wireless device, the second transmission request signalindicating that the first wireless device intends to send anothertraffic signal to a second wireless device different from the thirdwireless device, the second transmission request signal includinginformation indicative of a power ratio value 1204. The power ratiovalue may be recovered by the third device from the second transmissionrequest signal 1206. The power of the received first and secondtransmission request signals may be measured by the third device 1208.The power of the desired traffic signal to be received from the fourthwireless device may be predicted by the third device as a function ofthe measured power of the received first transmission request signal1210. Similarly, the power of the interfering traffic signal to betransmitted by the first wireless device may be predicted by the thirddevice as a function of the measured power of the received secondtransmission request signal and the recovered power ratio value 1212.The third device may then determine whether to receive the trafficsignal from the fourth wireless device as a function of the predictedpowers of the desired and interfering traffic signals 1214. If the thirddevice determines that it can receive the traffic signal from the fourthwireless device it may send a request response signal to the fourthwireless device 1216. The predicted power of the interfering trafficsignal may be equal to the measured power of the received secondtransmission request signal multiplied by the recovered power ratiovalue. The decision of whether to receive the traffic signal from thefourth wireless device may be determined as a function of ratio betweenthe predicted powers of the desired and interfering traffic signals.

Method of Using Flash Signaling to Allow Low-Priority Transmitter to notTransmit Yield to High-Priority Traffic

According to another example, devices within a peer-to-peer network mayundertake yielding decisions based on packet length informationascertainable from pilot signals. A first device WT A may wish totransmit a small packet to a second device WT B via a first peer-to-peerconnection while a third device WT C may wish to transmit a normalpacket to a fourth device WT D.

Again consider the baseline interference management protocol discussedin FIGS. 2, 3, 5, and 6. A traffic slot consists of a traffic management(or traffic control) channel portion and a traffic channel portion. Thetraffic channel portion is used to send actual data traffic, while thetraffic control channel portion is used by the terminals for managinginterference among them. Consider the scenario where a first terminalWT-A intends to send traffic to a second terminal WT-B and a thirdterminal WT-C intends to send traffic to fourth terminal WT-D. Furtherassume that traffic transmissions from the first to second terminals isof higher priority than traffic transmissions from the third to fourthterminals traffic so the third terminal WT C (low-priority transmitter)has to make sure the interference it would generate to the secondterminal WT-B (high-priority receiver) is acceptable, otherwise, thethird terminal WT-C has to restrain (i.e., transmit yield) from sendingthe traffic to the fourth terminal WT-D in the present traffic slot.

In order to make transmit yielding decision, the third terminal WT-Cestimates the “interference cost” to the second terminal WT-B. The“interference cost” is a function of the transmission power that thethird terminal WT-C intends to use to send the traffic to the fourthterminal WT-D. The third terminal WT-C may reduce its transmission powerto reduce the interference cost so that it does not need to yield to thetraffic from first to the second terminals WT-A and WT-B.

According to one feature, the “interference cost” may also be a functionof the signaling format. Two signaling formats are considered. The firstsignaling format is a Gaussian signaling format, in which the signaloccupies all the degrees of freedom. The second signaling format is anon-Gaussian signaling format, referred to as a “flash signaling”format, in which the signal occupies a small fraction, e.g., 10%, of thetotal degrees of freedom. For example, consider the scenario where thetraffic channel portion includes a number of OFDM symbols, each OFDMsymbol including a number of tones. With the Gaussian signaling format,the signal is transmitted in all the tones of all the OFDM symbols. Forexample, the transmitter terminal may transmit a complex symbol, e.g.,QPSK symbol, in every tone of every OFDM symbol. On the other hand, withthe flash signaling format, the signal is transmitted in a smallfraction of tones in some OFDM symbols. For example, the signal may betransmitted in only one tone in every OFDM symbol.

The interference cost calculated by third terminal WT C may depend onwhether the Gaussian or flash signaling format is to be used for thetraffic from the third to the fourth terminals. In particular, theinterference cost is lower when flash signaling format is used. In otherwords, assuming everything else equal, using flash signaling format, thethird terminal WT-C will need to yield less often. In one embodiment,the third terminal WT-C monitors (a traffic management channel) todetermine the number of other high-priority connections that are goingto use flash signaling format in the traffic channel of the presenttraffic slot. If the number is large, e.g., greater than three, thethird terminal WT-C may decide to yield (i.e., not transmit its trafficin the current traffic slot).

FIG. 13 (comprising FIGS. 13A and 13B) illustrates a method operationalin a third device having a peer-to-peer connection with a fourth deviceto facilitate interference management for a second peer-to-peerconnection between a first device and a second device within a wirelessnetwork. The third device may determine a signaling format to be usedfor a traffic signal to be sent to the fourth device, the signalingformat being one of at least Gaussian signaling format and flashsignaling format 1302. A transmission request signal is sent by thethird device to the fourth device in a transmission request resource1304. The third device monitors a transmission request response resourceto receive a first transmission request response from the second device,the transmission request response from the second device indicating thatthe second device is prepared to receive a traffic signal from the firstdevice different from the third device 1306. An interference cost to thesecond device may be calculated by the third device as a function of thedetermined signaling format 1308. The third device can then determinewhether to send the traffic signal to the fourth device based on thecalculated interference cost, the traffic signal to be sent in a trafficslot corresponding to the transmission request signal 1310. The thirddevice may monitor a transmission request response resource to receive asecond transmission request response from the fourth device, the secondtransmission request response from the fourth device indicating that thefourth device is prepared to receive a traffic signal from the thirddevice 1312. The third device can then determine whether the prioritycorresponding to the first transmission request response received fromthe second device is higher than the second transmission requestresponse received from the fourth device 1314.

According to one alternative, the third device may then send the trafficsignal in the traffic slot if it is determined that the calculatedinterference cost is below a threshold 1316. The value of calculatedinterference cost is smaller if it is determined that a flash signalingformat is to be used rather than if it is determined that a Gaussiansignaling format is to be used. The traffic signal is sent in a fractionof the traffic channel resource in the traffic slot if it is determinedthe flash signaling format is to be used. The fraction may be less thantwenty percent of the traffic channel.

According to one feature, the transmission request signal may includeinformation indicative of the signaling format to be used in the trafficsignal. The transmission request signal may be sent using a plurality oftones and information indicative of the signaling format to be used inthe traffic signal is sent using the phases of the plurality of tones.The number of information bits to be sent in the traffic signal when theGaussian signaling format is used may be at least twice as many as thenumber of information bits to be sent in the traffic signal when theflash signaling format is used.

According to another alternative, the third device may change thesignaling format from the Gaussian signaling format to the flashsignaling format if it is determined that the calculated interferencecost is sufficiently high that the third device is restrained fromsending the traffic signal to the fourth device if the third device isto use the Gaussian signaling format 1318. The third device may thensend the traffic signal in the traffic slot using the flash signalingformat 1320.

According to another alternative, the third device may monitortransmission request response resources to determine the number ofdevices that intend to use the flash signaling format in the trafficchannel of the traffic slot 1322. The third device may then restrainingfrom using the flash signaling format if it is determined that thenumber of devices that intend to use the flash signaling format in thetraffic channel of the traffic slot exceeds a threshold number 1324.

Method of Using Flash Signaling to Allow Low-Priority Receiver to notReceive Yield to High-Priority Traffic

According to another scenario, a first terminal WT-A intends to sendtraffic to a second terminal WT-B and a third terminal WT-C intends tosend traffic to fourth terminal WT-D. This example, assumes that thetraffic from the first terminal to the second terminal is of higherpriority than traffic from the third terminal to the fourth terminal.Therefore, the fourth terminal (low-priority receiver) has to make surethe interference from first terminal (high-priority transmitter) isacceptable; otherwise, the fourth terminal does not respond to thetransmission request from third terminal WT-C so that third terminalWT-C will not send the traffic to the fourth terminal WT-D in thecurrent traffic slot, i.e., perform receiver yielding.

In order to make a receiver yielding decision, the fourth terminal WT-Destimates the “signal to interference ratio” where the signal power isassociated with the signal to be sent by the third terminal WT-C and theinterference power is associated with the signal to be sent by firstterminal WT-A. The interference power may be obtained as a function ofthe received power of a transmission request that is sent by firstterminal WT-A to the second terminal WT-B but received at fourthterminal WT-D. Moreover, the interference power is also a function ofthe signaling format, e.g., Gaussian versus flash signaling formats.

According to one feature, the interference power calculated by fourthterminal WT-D may depend on whether the Gaussian or flash signalingformat is to be used for the traffic from the first terminal WT-A to thesecond terminal WT-B. In particular, the interference power may be lowerwhen flash signaling format is used. In other words, assuming everythingelse equal, if the first terminal WT-A is going to use flash signalingformat, the fourth terminal WT-D will need to yield less often. In oneembodiment, the fourth terminal WT-D monitors to see the number of otherhigh-priority connections that are going to use flash signaling formatin the traffic channel of the current traffic slot. If the number islarge, e.g., greater than three, the fourth terminal WT-D may decide toyield.

FIG. 14 (comprising FIGS. 14A and 14B) illustrates a method operationalin a fourth device having a peer-to-peer connection with a third deviceto facilitate interference management for a second peer-to-peerconnection between a first device and a second device within a wirelessnetwork. The fourth device may monitor to receive a first transmissionrequest signal from the third device and a second transmission requestsignal from the first device, the first transmission request signalindicating that the third device intends to send a traffic signal to thefourth device in a traffic slot corresponding to the first transmissionrequest signal and the second transmission request signal indicatingthat the first device intends to send a traffic signal to the seconddevice in the same traffic slot, the second transmission request signalfurther including information indicative of the signaling format to beused in the traffic signal from the first device to the second device,the signaling format being one of at least a Gaussian signaling formatand a flash signaling format 1402. The information indicative of thesignaling format may be recovered by the fourth device from the secondtransmission request signal 1404. The fourth device may then calculatean interference power as a function of the signal strength of thereceived second transmission request 1406. The value of the calculatedinterference power may be determined as a function of the recoveredsignaling format.

The value of the calculated interference power is smaller if the flashsignaling format is to be used than if the Gaussian signaling format isto be used. The traffic signal is to be sent by the first device in afraction of the traffic channel resource in the traffic slot if theflash signaling format is to be used. The fraction may be less thantwenty percent of the traffic channel. The second transmission requestsignal may be sent using a plurality of tones and the informationindicative of the signaling format to be used in the traffic signal issent using the phases of the plurality of tones.

The fourth device may then determine whether to receive the trafficsignal from the third device based on the calculated interference power1408. In making such determination, the fourth device may take a numberof steps. For example, the fourth device may further determine whetherthe priority corresponding to the second transmission request is higherthan the first transmission request 1410. The fourth device may alsomonitor transmission request resources to determine the number ofdevices that intend to use the flash signaling format in the trafficchannel of the traffic slot. If the fourth device determines that thenumber of devices that intend to use the flash signaling format in thetraffic channel of the traffic slot exceeds a threshold number, it mayrestrain from sending the transmission request response 1414.

The fourth device may also calculate a desired signal power as afunction of the signal strength of the received first transmissionrequest 1416. A transmission request response signal may be sent by thefourth device to the third device if it is determined that the ratio ofthe calculated desired signal power and the calculated interferencepower exceeds a threshold 1418. Subsequently, the fourth device mayreceive the traffic signal in the traffic slot 1420. The number ofinformation bits to be sent in the traffic signal when the Gaussiansignaling format is used are at least twice as many as the number ofinformation bits to be sent in the traffic signal when the flashsignaling format is used.

Channel Estimation (Pilot and CQI Channel) Design with Flash Signaling

The typical rate scheduling algorithm is split into two stages orphases. In a first stage, the transmitter first device WT A sends apilot signal over a pilot channel which is used by the receiver seconddevice WT B for SINR estimation. The receiver then sends back quantizedSINR value in a channel quality indicator (CQI) channel to thetransmitter first device WT A so that the transmitter first device WT Acan decide the rate format that should be used for the traffic datatransmission.

The first device WT A transmits a packet using Gaussian signaling to thesecond device WT B and the third device WT C transmits a small packet tothe fourth device WT D using non-Gaussian signaling or flash signaling.

There are two objectives for the rate scheduling stage. First, thefourth device WT D should be informed that the third device WT C has asmall packet and is using non-Gaussian (flash) signaling. The second isthat the SINR calculation done by the second device WT B shouldaccurately take into account the fact the transmission from the thirddevice WT C that acts as interference (to the transmission from thefirst device WT A) is using non-Gaussian signaling. This means that theif the traffic signal from the third device WT C is received at a highpower at the second device WT B, then such interference will act aserasures, otherwise it will act as additive noise.

For this purpose, a hybrid rate signaling scheme is used for the pilotchannel. The main idea is to mimic the signaling used for traffic datacommunications during the pilot channel. That is, the first device WT Awhich is using the usual Gaussian signaling for traffic communication,sends a pseudo-random noise (PN) sequence occupying the entire degreesof freedom used for the pilot channel, whereas the third device WT Cwhich is using non-Gaussian signaling uses a proportionate number ofhigh energy tones within the pilot channel.

One example may assume that the pilot channel consists of 128 complexdegrees of freedom. Then, the first device WT A transmits atpseudo-random noise sequence of length 128, this sequence is known tothe second device WT B. The third device WT C transmits a small number(2-4) of high energy tones. The tone locations may be pickedpseudo-randomly and are known to the fourth device WT-D.

The second device WT B may first determine the set of high energy tonesamongst received 128 tones. For example, this can be defined as tonesthat are at least 10 db higher than the average energy. Then, if thisset of tones includes that set of tones that the first device WT A wouldhave used if it had a small packet (which is known to the second device)then the second device WT B assumes that the first device WT A has asmall packet to send, and sends back a default message (typicallycorresponding to the lowest rate option) back to the first device WT Aduring the CQI channel. Otherwise, the second device WT B discards thesetones as erasures, and uses the remaining tones for SINR estimation.After calculating the SINR for the remaining tones, it accounts for thenumber of tones lost as erasures to calculate an effective (lower) SINRthat is quantized and sent back to the first device WT A during the CQIchannel. The fourth device WT-D behaves similar to the second device WTB.

FIG. 15 illustrates a method of operating a second wireless device in apeer-to-peer communication network, the second wireless device having aconnection with a transmitter first wireless device. The second device(WT-B or WT-D) may monitor to receive a pilot signal from the firstdevice in a pilot channel associated with a data traffic slot 1502. Thesecond device may determine a pilot format being used by the firstdevice based on the received pilot signal 1504. To achieve this, thesecond device may determine a fraction of the transmission resource inthe pilot channel to be used by the first device assuming that the pilotformat used by the first device corresponds to a flash signaling datatraffic format 1506. It may also measure the average power of the pilotsignal in the fraction of the transmission resource in the pilot channeland the average power of the pilot signal in the entire pilot channel1508. If the measured average power on the fraction of transmissionresource is at least 10 dB stronger than the measured average power inthe pilot channel, the second device may determine that the pilot formatused by the second device corresponds to a flash signaling data trafficformat 1510.

The second device can then determine a data traffic format to be used inthe data transmission slot based on the determined pilot format 1512.The data traffic format may be one of a flash signaling data trafficformat and a Gaussian signaling data traffic format. When the pilotformat corresponding to flash signaling data traffic format is used, thepilot signal from the second device is sent on a fraction oftransmission resource of the entire pilot channel. The fraction of thepilot channel used may be less than twenty percent. Additionally, thefraction of the pilot channel used is the same as the fraction oftransmission resource of the flash signaling data traffic format in thedata traffic slot. This relationship in the protocol is used by thesecond device to determine that the same fraction will be used in thedata traffic slot as it is in the pilot channel.

The interference power can be calculated by the second device based onthe determined pilot format and received pilot signal 1514. Incalculating the interference power, the second device may determine afraction of transmission resources in the pilot channel over which themeasured average received power is at least 10 dB stronger than themeasured average power in the pilot channel, where the calculatedinterference power is calculated based on the received signal in theremaining fraction of transmission resources in the pilot channel 1516.

A data rate can then be determined by the second device based on thecalculated interference power and the determined data traffic format1518.

Add Power Backoff Information for Small Packet Devices with RateFeedback (CQI Channel)

A typically CQI channel is designed to carry number of bits thatcorresponds to the total number rate options that the system supports(typically 3-4 bits). But, for a small packet format, the number ofpossible rate options is fairly small. Thus, according to one feature,the additional available bits are used to indicate power backoff thatthe transmitter device should use without hurting the reliability of thetransmission significantly.

A first device WT A intends to transmit a small packet to a seconddevice WT B over a peer-to-peer network connection. Let's assume thatCQI channel supports 4 bits, and there is just one rate optioncorresponding to the small packet mode. Either through a link schedulingstage or during the pilot transmission, the second device WT B is madeaware that the first device WT A has a small packet for transmission.

The first device WT A sends a pilot signal to the second device WT Bover the pilot channel. The second device WT B uses the pilot signal toobtain a SINR estimation. If the SINR measured, SINR_m, is more than theSINR needed for transmission of a small packet, SINR_s, then the firstdevice WT A can lower the power used for the data transmission by afactor of SINR_m/SINR_s. Therefore, the second device WT B may quantizeSINR_m/SINR_s to 4 bits, and sends these 4 bits on the CQI channel. Thefirst device WT A interprets these bits as power backoff bits ratherthan rate option bits since it knows the transmission is a small packettransmission.

FIG. 16 illustrates a method of operating a second wireless device in apeer-to-peer communication network, where the second wireless device hasa connection with a transmitter first wireless device. The second devicereceives a pilot signal from the second device in a pilot channelassociated with a data traffic slot 1602. A data transmission format tobe used in the data traffic slot is then determined by the seconddevice, where the data transmission format includes at least a smallpacket format and a normal packet format 1604. If the second devicedetermines that the data transmission format to be used in the datatraffic slot is a small packet format, it may determine an amount ofpower back off based on at least the pilot signals received in the pilotchannel, the power back off indicating the amount that the secondwireless device can reduce for the transmission power of the datatraffic slot 1606.

A rate feedback format to be used in a rate feedback channel associatedwith the data traffic slot may then be determined by the second devicebased on the determined data transmission format 1608. The second devicethen sends a rate feedback signal in the rate feedback channel using therate feedback format 1610. It may also signal the determined amount ofpower back off in the rate feedback signal 1612. The rate feedbacksignal may contain information indicative of a rate selected from aplurality of predetermined rates in a rate table, the rate table being afunction of the determined data transmission format. The number of ratesin the rate table may be smaller when the data transmission format is asmall packet format than when the data transmission format is a normalpacket format. The data transmission format may be determined based oninformation contained in the pilot signal.

FIG. 17 is a block diagram of a first wireless terminal that may beconfigured to facilitate peer-to-peer communications with a secondwireless terminal over a shared frequency spectrum. The wirelessterminal 1702 may include a processing circuit 1704 (e.g., one or morecircuits or processors), a peer-to-peer communication controller 1712, awide area network (WAN) controller 1710 and a transceiver 1714 coupledto at least one antenna 1706. The transceiver 1714 may include a(wireless) transmitter and a (wireless) receiver. The wireless terminal1702 may communicate via a managed network infrastructure using the WANcommunication controller 1210 and/or it may communicate over apeer-to-peer network using the peer-to-peer communication controller1712. When performing peer-to-peer communications, the first wirelessterminal 1702 may be configured to perform one or more of the featuresillustrated in FIGS. 1-16.

While described in the context of an OFDM TDD system, the methods andapparatus of various embodiments are applicable to a wide range ofcommunications systems including many non-OFDM, many non-TDD systems,and/or many non-cellular systems.

In various embodiments nodes described herein are implemented using oneor more modules to perform the steps corresponding to one or moremethods, for example, generating a beacon signal, transmitting a beaconsignal, receiving beacon signals, monitoring for beacon signals,recovering information from received beacon signals, determining atiming adjustment, implementing a timing adjustment, changing a mode ofoperation, initiating a communication session, etc. In some embodimentsvarious features are implemented using modules. Such modules may beimplemented using software, hardware or a combination of software andhardware. Many of the above described methods or method steps can beimplemented using machine executable instructions, such as software,included in a machine readable medium such as a memory device, e.g.,RAM, floppy disk, etc. to control a machine, e.g., general purposecomputer with or without additional hardware, to implement all orportions of the above described methods, e.g., in one or more nodes.Accordingly, among other things, various embodiments are directed to amachine-readable medium including machine executable instructions forcausing a machine, e.g., processor and associated hardware, to performone or more of the steps of the above-described method(s).

Numerous additional variations on the methods and apparatus describedabove will be apparent to those skilled in the art in view of the abovedescriptions. Such variations are to be considered within scope. Themethods and apparatus of various embodiments may be, and in variousembodiments are, used with CDMA, orthogonal frequency divisionmultiplexing (OFDM), and/or various other types of communicationstechniques which may be used to provide wireless communications linksbetween access nodes and mobile nodes. In some embodiments the accessnodes are implemented as base stations which establish communicationslinks with mobile nodes using OFDM and/or CDMA. In various embodimentsthe mobile nodes are implemented as notebook computers, personal dataassistants (PDAs), or other portable devices includingreceiver/transmitter circuits and logic and/or routines, forimplementing the methods of various embodiments.

One or more of the components, steps, and/or functions illustrated inFIGS. 1-17 may be rearranged and/or combined into a single component,step, or function or embodied in several components, steps, orfunctions. Additional elements, components, steps, and/or functions mayalso be added. The apparatus, devices, and/or components illustrated inFIGS. 1, 2, and/or 17 may be configured or adapted to perform one ormore of the methods, features, or steps described in FIGS. 3-16. Thealgorithms described herein may be efficiently implemented in softwareand/or embedded hardware.

Those of skill in the art would further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the configurations disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system.

The various features described herein can be implemented in differentsystems. For example, the secondary microphone cover detector may beimplemented in a single circuit or module, on separate circuits ormodules, executed by one or more processors, executed bycomputer-readable instructions incorporated in a machine-readable orcomputer-readable medium, and/or embodied in a handheld device, mobilecomputer, and/or mobile phone.

It should be noted that the foregoing configurations are merely examplesand are not to be construed as limiting the claims. The description ofthe configurations is intended to be illustrative, and not to limit thescope of the claims. As such, the present teachings can be readilyapplied to other types of apparatuses and many alternatives,modifications, and variations will be apparent to those skilled in theart.

1. A method operational at a second device having a peer-to-peerconnection with a first device to facilitate interference management ofsmall packet transmissions in an ad hoc wireless network, comprising:receiving a signal in a plurality of predetermined subsets of resourceunits, said resource units being time-frequency resource units, at leastsome of said time-frequency resource units corresponding to differenttones; calculating a first signal phase used in a desired signal in eachof the plurality of predetermined subsets of resource units, the desiredsignal being sent by the first device; and determining onetime-frequency resource unit in each of the plurality of predeterminedsubsets of resource units in which the desired signal is sent as afunction of the received signal and calculated first signal phase. 2.The method of claim 1, further comprising: recovering information bitstransported in the desired signal from the location of the determinedone time-frequency resource unit in each of the plurality ofpredetermined subsets of resource units.
 3. The method of claim 2,wherein the calculated first signal phase is the same in each of theplurality of predetermined subsets of resource units and is generatedfrom at least one of a first identifier of the first device, a secondidentifier of the second device, and an identifier of the peer-to-peerconnection between the first and the second devices.
 4. The method ofclaim 2, wherein the calculated first signal phase is determined as afunction of a predetermined sequence, the calculated first signal phasebeing different in the different predetermined subsets of resourceunits.
 5. The method of claim 4, wherein the predetermined sequence isgenerated from at least one of a first identifier of the first device, asecond identifier of the second device, and an identifier of thepeer-to-peer connection between the first and the second devices.
 6. Themethod of claim 2, further comprising: calculating a power to be used inthe desired signal in each of the plurality of predetermined subsets ofresource units, wherein the calculated power is determined as a functionof a predetermined sequence, the calculated power being different in thedifferent predetermined subsets of resource units, and wherein the onetime-frequency resource unit is determined also as a function of thecalculated power.
 7. The method of claim 1, further comprising:calculating a second phase to be used in an interference signal in eachof the plurality of predetermined subsets of resource units, theinterference signal being transmitted by an interfering device; andwherein the one time-frequency resource unit is determined also as afunction of the calculated second phase.
 8. A second device having apeer-to-peer connection with a first device to facilitate interferencemanagement of small packet transmissions in an ad hoc wireless network,comprising: a transmitter and receiver for establishing the peer-to-peercommunication connection with the first device; a processing circuitcoupled to the transmitter and receiver, wherein the processing circuitis adapted to: receive a signal in a plurality of predetermined subsetsof resource units, said resource units being time-frequency resourceunits, at least some of said time-frequency resource units correspondingto different tones; calculate a first signal phase used in a desiredsignal in each of the plurality of predetermined subsets of resourceunits, the desired signal being sent by the first device; and determineone time-frequency resource unit in each of the plurality ofpredetermined subsets of resource units in which the desired signal issent as a function of the received signal and calculated first signalphase.
 9. The second device of claim 8, wherein the processing circuitis further adapted to: recover information bits transported in thedesired signal from the location of the determined one time-frequencyresource unit in each of the plurality of predetermined subsets ofresource units.
 10. The second device of claim 9, wherein the calculatedfirst signal phase is the same in each of the plurality of predeterminedsubsets of resource units and is generated from at least one of a firstidentifier of the first device, a second identifier of the seconddevice, and an identifier of the peer-to-peer connection between thefirst and the second devices.
 11. The second device of claim 9, whereinthe calculated first signal phase is determined as a function of apredetermined sequence, the calculated first signal phase beingdifferent in the different predetermined subsets of resource units. 12.The second device of claim 11, wherein the predetermined sequence isgenerated from at least one of a first identifier of the first device, asecond identifier of the second device, and an identifier of thepeer-to-peer connection between the first and the second devices. 13.The second device of claim 9, wherein the processing circuit is furtheradapted to: calculate a power to be used in the desired signal in eachof the plurality of predetermined subsets of resource units, wherein thecalculated power is determined as a function of a predeterminedsequence, the calculated power being different in the differentpredetermined subsets of resource units, and wherein the onetime-frequency resource unit is determined also as a function of thecalculated power.
 14. The second device of claim 8, wherein theprocessing circuit is further adapted to: calculate a second signalphase to be used in an interference signal in each of the plurality ofpredetermined subsets of resource units, the interference signal beingtransmitted by an interfering device; and wherein the one time-frequencyresource unit is determined also as a function of the calculated secondsignal phase.
 15. A second device having a peer-to-peer connection witha first device to facilitate interference management of small packettransmissions in an ad hoc wireless network, comprising: means forreceiving a signal in a plurality of predetermined subsets of resourceunits, said resource units being time-frequency resource units, at leastsome of said time-frequency resource units corresponding to differenttones; means for calculating a first signal phase to be used in adesired signal in each of the plurality of predetermined subsets ofresource units, the desired signal being sent by the first device; andmeans for determining one time-frequency resource unit in each of theplurality of predetermined subsets of resource units in which thedesired signal is sent as a function of the received signal andcalculated first signal phase.
 16. The second device of claim 15,further comprising: means for recovering information bits transported inthe desired signal from the location of the determined onetime-frequency resource unit in each of the plurality of predeterminedsubsets of resource units.
 17. The second device of claim 16, whereinthe calculated first signal phase is the same in each of the pluralityof predetermined subsets of resource units and is generated from atleast one of a first identifier of the first device, a second identifierof the second device, and an identifier of the peer-to-peer connectionbetween the desired and the second devices.
 18. The second device ofclaim 16, further comprising: means for calculating a power to be usedin the desired signal in each of the plurality of predetermined subsetsof resource units, wherein the calculated power is determined as afunction of a predetermined sequence, the calculated power beingdifferent in the different predetermined subsets of resource units, andwherein the one time-frequency resource unit is determined also as afunction of the calculated power.
 19. The second device of claim 16,further comprising: means for calculating a second signal phase to beused in an interference signal in each of the plurality of predeterminedsubsets of resource units, the interference signal being transmitted byan interfering device, and wherein the one time-frequency resource unitis also determined as a function of the calculated second signal phase.20. A non-transitory machine-readable medium comprising instructions fora second device having a peer-to-peer connection with a first device tofacilitate interference management of small packet transmissions in anad hoc wireless network, which when executed by a processor causes theprocessor to: receive a signal in a plurality of predetermined subsetsof resource units, said resource units being time-frequency resourceunits, at least some of said time-frequency resource units correspondingto different tones; calculate a first signal phase to be used in adesired signal in each of the plurality of predetermined subsets ofresource units, the desired signal being sent by the first device; anddetermine one time-frequency resource unit in each of the plurality ofpredetermined subsets of resource units in which the desired signal issent as a function of the received signal and calculated first signalphase.
 21. A method operational at a first device having a peer-to-peerconnection with a second device to facilitate interference management ofsmall packet transmissions within an ad hoc wireless network,comprising: partitioning a set of resource units into a plurality ofpredetermined subsets of resource units, said resource units beingtime-frequency resource units, at least some of said time-frequencyresource units corresponding to different tones; determining onetime-frequency resource unit in each of the plurality of predeterminedsubsets of resource units as a function of a set of bits; andtransmitting signals using the determined time-frequency resource units,each signal transmitted in one of the determined time-frequency resourceunits having a signal phase, the signal phase of each of the signalstransmitted using the determined time-frequency resource units in saidplurality of predetermined subsets of resource units, being the same.22. The method of claim 21, wherein the set of bits are generated from aset of information bits with an encoder.
 23. The method of claim 22,wherein the signal phase is generated from at least one of a firstidentifier of the first device, a second identifier of the seconddevice, and an identifier of the peer-to-peer connection between thefirst and the second devices.
 24. A method operational at a first devicehaving a peer-to-peer connection with a second device to facilitateinterference management of small packet transmissions within an ad hocwireless network, comprising: partitioning a set of resource units intoa plurality of predetermined subsets of resource units; determining oneresource unit in each of the plurality of predetermined subsets ofresource units as a function of a set of bits, said set of bits beinggenerated from a set of information bits with an encoder; transmitting asignal in the determined one resource unit in each of the plurality ofpredetermined subsets of resource units; and generating a plurality ofphases as a function of a predetermined sequence, wherein a phase of thetransmitted signal in the determined one resource unit in each of theplurality of predetermined subsets of resource units is equal to one ofthe generated plurality of phases.
 25. The method of claim 24, whereinthe predetermined sequence is generated from at least one of a firstidentifier of the first device, a second identifier of the seconddevice, and an identifier of the peer-to-peer connection between thefirst and the second devices.
 26. The method of claim 22, furthercomprising: generating a plurality of power values as a function of apredetermined sequence, wherein the power of the transmitted signal inthe determined one time-frequency resource unit in each of the pluralityof predetermined subsets of resource units is equal to one of thegenerated plurality of power values.
 27. A first device having apeer-to-peer connection with a second device to facilitate interferencemanagement of small packet transmissions within an ad hoc wirelessnetwork, comprising: a transmitter and receiver for establishing thepeer-to-peer communication connection with the first device; aprocessing circuit coupled to the transmitter and receiver, wherein theprocessing circuit is adapted to: partition a set of resource units intoa plurality of predetermined subsets of resource units, said resourceunits being time-frequency resource units, at least some of saidtime-frequency resource units corresponding to different tones;determine one time-frequency resource unit in each of the plurality ofpredetermined subsets of resource units as a function of a set of bits;and transmit signals using the determined time-frequency resource units,each signal transmitted in one of the determined time-frequency resourceunits having a signal phase, the signal phase of each of the signalstransmitted using the determined time-frequency resource units in saidplurality of predetermined subsets of resource units, being the same.28. The first device of claim 27, wherein the set of bits are generatedfrom a set of information bits with an encoder.
 29. The first device ofclaim 28, wherein the signal phase is generated from at least one of afirst identifier of the first device, a second identifier of the seconddevice, and an identifier of the peer-to-peer connection between thefirst and the second devices.
 30. A first device having a peer-to-peerconnection with a second device to facilitate interference management ofsmall packet transmissions within an ad hoc wireless network,comprising: a transmitter and receiver for establishing the peer-to-peercommunication connection with the first device; a processing circuitcoupled to the transmitter and receiver, wherein the processing circuitis adapted to: partition a set of resource units into a plurality ofpredetermined subsets of resource units; determine one resource unit ineach of the plurality of predetermined subsets of resource units as afunction of a set of bits, said set of bits being generated from a setof information bits with an encoder; transmit a signal in the determinedone resource unit in each of the plurality of predetermined subsets ofresource units; and generate a plurality of phases as a function of apredetermined sequence, wherein a phase of the transmitted signal in thedetermined one resource unit in each of the plurality of predeterminedsubsets of resource units is equal to one of the generated plurality ofphases.
 31. The first device of claim 30, wherein the predeterminedsequence is generated from at least one of a first identifier of thefirst device, a second identifier of the second device, and anidentifier of the peer-to-peer connection between the first and thesecond devices.
 32. The first device of claim 28, wherein the processingcircuit is adapted to: generate a plurality of power values as afunction of a predetermined sequence, wherein the power of thetransmitted signal in the determined one time-frequency resource unit ineach of the plurality of predetermined subsets of resource units isequal to one of the generated plurality of power values.
 33. A firstdevice having a peer-to-peer connection with a second device tofacilitate interference management of small packet transmissions withinan ad hoc wireless network, comprising: means for partitioning a set ofresource units into a plurality of predetermined subsets of resourceunits, said resource units being time-frequency resource units, at leastsome of said time-frequency resource units corresponding to differenttones; means for determining one time-frequency resource unit in each ofthe plurality of predetermined subsets of resource units as a functionof a set of bits; and means for transmitting signals using thedetermined time-frequency resource units, each signal transmitted in oneof the determined time-frequency resource units having a signal phase,the signal phase of each of the signals transmitted using the determinedtime-frequency resource units in said plurality of predetermined subsetsof resource units, being the same.
 34. The first device of claim 33,wherein the signal phase is generated from at least one of a firstidentifier of the first device, a second identifier of the seconddevice, and an identifier of the peer-to-peer connection between thefirst and the second devices.
 35. A first device having a peer-to-peerconnection with a second device to facilitate interference management ofsmall packet transmissions within an ad hoc wireless network,comprising: means for partitioning a set of resource units into aplurality of predetermined subsets of resource units; means fordetermining one resource unit in each of the plurality of predeterminedsubsets of resource units as a function of a set of bits; means fortransmitting a signal in the determined one resource unit in each of theplurality of predetermined subsets of resource units; and means forgenerating a plurality of phases as a function of a predeterminedsequence, wherein a phase of the transmitted signal in the determinedone resource unit in each of the plurality of predetermined subsets ofresource units is equal to one of the generated plurality of phases. 36.The method of claim 35, wherein the predetermined sequence is generatedfrom at least one of a first identifier of the first device, a secondidentifier of the second device, and an identifier of the peer-to-peerconnection between the first and the second devices.
 37. The method ofclaim 33, further comprising: means for generating a plurality of powervalues as a function of a predetermined sequence, wherein the power ofthe transmitted signal in the determined one time-frequency resourceunit in each of the plurality of predetermined subsets of resource unitsis equal to one of the generated plurality of power values.
 38. Anon-transitory machine-readable medium comprising instructions for afirst device having a peer-to-peer connection with a second device tofacilitate interference management of small packet transmissions withinan ad hoc wireless network, which when executed by a processor causesthe processor to: partition a set of resource units into a plurality ofpredetermined subsets of resource units, said resource units beingtime-frequency resource units, at least some of said time-frequencyresource units corresponding to different tones; determine onetime-frequency resource unit in each of the plurality of predeterminedsubsets of resource units as a function of a set of bits; and transmitsignals using the determined time-frequency resource units, each signaltransmitted in one of the determined time-frequency resource unitshaving a signal phase, the signal phase of each of the signalstransmitted using the determined time-frequency resource units in saidplurality of predetermined subsets of resource units, being the same.39. A non-transitory machine-readable medium comprising instructions fora first device having a peer-to-peer connection with a second device tofacilitate interference management of small packet transmissions withinan ad hoc wireless network, which when executed by a processor causesthe processor to: partition a set of resource units into a plurality ofpredetermined subsets of resource units; determine one resource unit ineach of the plurality of predetermined subsets of resource units as afunction of a set of bits, said set of bits being generated from a setof information bits with an encoder; transmit a signal in the determinedone resource unit in each of the plurality of predetermined subsets ofresource units; and generate a plurality of phases as a function of apredetermined sequence, wherein a phase of the transmitted signal in thedetermined one resource unit in each of the plurality of predeterminedsubsets of resource units is equal to one of the generated plurality ofphases.